micro midterm Flashcards
(433 cards)
1
Q
What is Microbiology?
A
- Specialized area of biology that studies living things too small to be seen without magnification.
2
Q
Microbiology
A
o Microbes
o Microorganisms
o Germs
o Bugs
3
Q
Branches of Microbiology
A
- Bacteriology
- Mycology
- Protozoology
- Virology
- Parasitology
- Phycology or Algology
4
Q
Bacteriology
A
the study of bacteria, a subdivision of microbiology involving:
- Identification
- Classification
- Characterization of bacterial species
5
Q
Mycology
A
the branch of biology concerned with the study of fungi, including their:
- Genetic properties
- Biochemical properties
- Taxonomy (the practice and study of classification of things)
6
Q
Protozoology
A
a branch of biology which studies a group of unicellular eukaryotic organisms.
7
Q
Virology
A
the study of viruses, their:
- Structure
- Classification
- Evolution
- Ways to infect and exploit host cells for reproduction
- Interaction with host organism physiology and immunity
8
Q
Parasitology
A
the study of parasites, their hosts, and the relationship between them.
9
Q
Phycology or Algology
A
the study of algae
10
Q
What Microbiology Studies
A
- Microbial Morphology
- Microbial Physiology
- Microbial Taxonomy
- Microbial Genetics, Molecular Biology
- Microbial Ecology
11
Q
Microbial Morphology
A
refers to the size, shape, and arrangement of bacteria
12
Q
Microbial Physiology
A
studies function of bacteria at the cellular and molecular levels
13
Q
Microbial Taxonomy
A
- Classification
- Naming
- Identification of microorganism
14
Q
Microbial Genetics, Molecular Biology
A
studies the function of genetic material and the biochemical reactions of cells involved in metabolism and growth.
15
Q
Microbial Ecology
A
studies interrelationships between microbes and the environment, the roles of microorganisms in the nutrient cycles of soil, water and other natural communities.
16
Q
Applied Microbiology
A
- Immunology
- Epidemiology
- Food Microbiology
- Agricultural Microbiology
- Industrial Microbiology
- Genetic Engineering
17
Q
Immunology
A
studies of the body’s defense that protect against infection.
18
Q
Epidemiology
A
studies how to monitor and control the spread of diseases in communities.
19
Q
Agricultural Microbiology
A
studies the relationship between microbes and crops, with an emphasis on improving yield and combating plant diseases. Uses microbes which are NOT harmful to humans to kill pests (insect and plant diseases). This rather than pesticides, is a safer and healthier way to increase crop yield.
20
Q
Industrial Microbiology
A
studies the use of microbes to produce or harvest large quantities of useful and necessary materials such as vitamins, amino acids, drugs, enzymes. Also for example, they can create bacteria, which will clean up an oil spill.
21
Q
Genetic Engineering
A
studies techniques that deliberately alter the genetic makeup of organisms to induce new compounds, different genetic combinations, and even unique organisms.
22
Q
Characteristics of Microorganisms
A
- Eukaryotic cells
- Prokaryotic cells
23
Q
Eukaryotic Cells
A
- “eu” means “true” or “good” nucleus
- Nucleus present
- Number of chromosomes – more than one
- True membrane bound nucleus – present
- Organelles (endoplasmic reticulum, lysosomes, mitochondria, Golgi apparatus) – present
- Cytoskeleton – present
- Ribosomes – larger
- Cell size – larger
- Examples: plant, animal, fungal cells
24
Q
Prokaryotic cells
A
- “pro” means “before” nucleus
- Nucleus absent
- Number of chromosomes – one, but not true chromosome (plasmids)
- True membrane bound nucleus – absent
- Organelles (endoplasmic reticulum, lysosomes, mitochondria, Golgi apparatus) – absent
- Cytoskeleton – may be absent
- Ribosomes – smaller
- Cell size – smaller
- Examples: bacteria
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Microorganisms are specified by:
- small size
- Unicellular
- Simplicity
- High Growth Rate
- High Rate of Adaptability
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- High Growth Rate
the growth rate of microorganisms is very high in a short time
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- High Rate of Adaptability
it is what allows microbes to cause diseases in the humans. They can do their harm to us, but our bodies cannot harm them because they are more adaptable that we are. Viruses have higher adaptability than bacteria.
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Simple Microscope
Contains just a single lens and a few working parts.
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Compound Microscope
- 2 magnifying lens
- Visible light
- A condenser (a special lens to converge or focus the rays of light to a single point on the object, it does NOT account for magnification).
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A microscope should provide adequate:
Magnification
Resolution
clarity of image
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- Magnification
capacity of an optical system to enlarge small objects
o Make object bigger
o Defines as the ability of a microscope to enlarge an object
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- Resolution
the capacity of optical system to distinguish or separate to adjacent objects or points from each other
o Distinguishing magnified object clearly
o Defines as the ability of a microscope to distinguish two adjacent points
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- Clarity of an image
smallest distance between two dots
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Objective Lens
- 4x low dry objective lens
- 10x dry objective lens
- 40x high dry objective lens
- 100x oil immersion objective lens
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Ocular Lens:
- 10x – 20x
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Total magnification
ocular lens x objective lens
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1. Light Microscopes
```
(the highest magnification is 2,000x and the resolution on them is 200 nm)
Light Field
Dark Field
Phase-contrast
Differential- Interference
```
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a. Bright-field light microscope
the best scope to see DEAD bacteria fixed on a slide
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b. Dark-field microscope
good for looking at the living bacteria
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c. Phase-contrast microscope
good for looking at living microbes
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d. Differential interference microscope
good for looking at 3D, color, living microbes
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2. Ultra violet microscopes
use ultraviolet rays as source of illumination
| a. Fluorescent microscope has magnification 2,000x and resolution 0.2 micrometers
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3. Electron Microscope
electron beam forms image of specimen.
- Transmssion
- Scanning Electron
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a. Transmission electron microscope
magnification is about 1,000,000x and resolution is 0.5 nm (good for viewing viruses)
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b. Scanning electron microscope
magnification is about 100,000x and resolution is 10 nm
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- Prokaryotic cells
bacteria
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- Eukaryotic cells:
```
o Fungi
o Algae
o Protozoans
o Helminth worms
o Animal cells
o Plant cells
```
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Bacteria Prokaryotic Cells
1. Eubacteria: (more common bacteria):
| 2. Archaebacteria (less common):
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1. Eubacteria
a. Eubacteria (-) with cell wall
b. Eubacteria (+) with cell wall
c. Eubacteria with no cell wall (+ and -)
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2. Archaebacteria
a. Live in extreme environments (high temperature, high salt, or low pH)
b. Cannot grow in the human body, do not cause human pathology
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Prokaryotic Cells (structure)
1. Appendages
2. Cell Envelopes
3. Protoplasm
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1. Appendages:
a. Flagella
b. Axial filaments/endoflagella
c. Pili
d. Fimbriae
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2. Cell envelopes:
a. Glycocalyx (capsules, slime layers)
b. Cell wall
c. Cell membrane
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3. Protoplasm:
a. Cell pool
b. Ribosomes
c. Mesosomes
d. Granules
e. Nucleoid, aka. Chromatin bodies
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Appendages
```
- Those that provide motility:
o Flagella
o Axial filaments
- Those that provide attachments:
o Fimbriae
o Pilli
```
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Function of Flagella
o The primary role of the flagellum is locomotion (self-propulsion, smooth, forward movement)
o It also often has function as a sensory, being sensitive to chemicals and temperatures outside the cell
o Flagella is found mostly in Gram-negative bacteria, but in Gram-positive bacteria it can be found too.
57
Structure of Flagella
o Flagella is made of protein
o Flagella is composed of three distinct parts:
The filament (out of the bacteria)
The hook (attached to the bacteria)
The basal body (inside the bacteria)
o The basal body has two (Gram-positive) or four (Gram-negative) rings.
The rings rotate counter-clockwise, and the bacteria rotate clockwise
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Types of Flagella
o Monotrichous
o Lophotrichous
o Amphitrichous
o Peritrichous
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o Monotrichous
bacteria have a single flagellum, e.g. Vibrio cholerae
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o Lophotrichous
bacteria have multiple flagella, located at the same spot on the bacteria surface
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o Amphitrichous
bacteria have single flagellum on each of two opposite ends
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o Peritrichous
bacteria have flagella projecting in all directions, e.g. E. coli
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Axial Filaments
o Axial filament is the central often contractile filament of flagellum (a.k.a. endoflagellum)
o A type of modified flagellum that consists of a long, thin microfibril inserted into a hook
o Axial filaments are similar to flagella, except that they wrap around the cell.
o The microfibrils of the axial filament lies between the cell wall and the cell membrane
o These structures contract causing the slow jerky movements of the microfibrils
o Axial filaments are found mostly in Gram negative rod bacteria (e.g. spirochetes)
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Appendages of Attachment
- Pili and Fimbriae are made of protein; involved in attachment of acteria to the host cells.
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o Pili
refer to the long appendages, (e.g. E. coli)
- The primary function of pili are to attach a bacterial cell to specific surfaces or to other cells
- Pili can also aid in attachment between bacterial cells. Some bacteria are able to produce conjugation pili that allow for the transfer of DNA from one bacterial cell to another
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o Fimbriae
refer to short appendages, (e.g. Streptococci)
- A bacterium that has fimbriae is usually covered with short hair-life fibers
- In contrast, pili are much longer, and a cell usually only has one or two pili.
- Pathogenic bacteria can have adhesions on the fimbriae that allow them to attach to the target tissues of their host.
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Glycocalyx
bacterial surface coating, has a delicate :sugar coating:, composed of polysaccharides bound in various ways to proteins
- Not each bacteria has a glycocalyx, because it is not necessary for its survival
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- Two types of glycocalyx:
1. Slime Layer
| 2. Capsules
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1. Slime layer
prevents bacteria from phagocytosis, protects bacteria from loss of water and nutrients. Its loose shield can be washed off.
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2. Capsules
tightly bounded to cell wall and prevent bacteria from phagocytosis. It has thicker, gummy consistency and cannot be easily washed off.
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Cell Wall
the layer underneath the glycocalyx. It:
o Defines the shape of bacteria
o Protects bacteria (e.g. osmotic pressure)
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- Cell wall is composed of
peptidoglycan
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o Peptidoglycan is
a substance that provides the relatively rigid protective quality of the cell wall
o The amount of peptidoglycan varies among the general groups of bacteria
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- Gram positive cell wall:
o Thick sheet composed of numerous sheets of peptidoglycan (100-150 layers) and tightly bound acidic polysaccharides
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- Gram negative cell wall:
o Contains an outer membrane lipopolysaccharides (40-50 layers)
o A thin sheet of peptidoglycan (3-5 layers)
o An extensive space between outer membrane and peptidoglycan, and peptidoglycan and cell membrane
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Gram Staining
- It is a stain for bacteria with cell wall.
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primary stain
Crystal Violet
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Mordant (fixing agent)
Iodine
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Washing Solution (decolorizer)
Alcohol
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Secondary Stain (counterstain)
Safranin
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Gram +
PURPLE
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Gram --
RED
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Acid fast staining
- The acid fast stain is a technique that differentiates Mycobacterium species from other bacteria
- The cell walls of the mycobacteria contain mycolic acids giving the cell walls a high lipid content. These bacteria are difficult to Gram stain.
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- Acid fast positive
RED
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- Acid fast negative
PURPLE
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Cell Membrane
(a. k.a. cytoplasmic membrane, plasma membrane) is very thin flexible sheet molded completely around the cytoplasm
- Made of phospholipids and proteins (fluid mosaic model)
- Responsible for flexibility, permeability and transport (of nutrients, water etc.)
- Site of metabolic activity (biosynthesis and degradation)
- Energy reactions
- Synthesis (macromolecules, lipid, nucleic acid)
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Protoplasm
the internal content of the cell, and represents a dense, gelatinous solution inside the bacterial envelope.
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- Contents of cell protoplasm
```
o Cytoplasm (a.k.a. cell “pool”) – is the major component of the cell. Composed of water, sugar, amino acids, salts
o Chromatin body (bacteria chromosome) – bacteria do not have a true nucleus and their DNA is not enclosed by a nuclear membrane. DNA is aggregated in a central area of the cell called the NUCLEOID.
```
89
- Plasmids
are nonessential pieces of DNA which confers protective traits upon bacteria (extrachromosomal DNA), are capable of replication, and may be transferred to another cell, with confers a resistance to antibiotic treatment.
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- Ribosomes
tiny special type of RNA which synthesize proteins
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- Mesosomes
are areas of the cell membrane which fold up into the cytoplasm and increase the internal surface for membrane function. Additionally, it functions in DNA replication, cell division, secretion
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- Granules
storage of energy rich bodies
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Two types of granules:
o Membrane-bound granules
| o Non-Membrane-bound granules
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o Membrane-bound granules
for storage of organic compounds (such as glycogen or starch)
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o Non-Membrane-bound granules
for storage of inorganic compounds (such as iron or other metals, sulfur and iodine)
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Bacterial Morphology
o Shape
o Size
o Arrangement
o Specific structure of bacteria
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Bacterial Shape
- coccus
- baccilus/rod
- spirillum
- spirochete
- vibrio
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- Coccus
any microorganism (usually bacteria) whose overall shape is spherical or nearly spherical
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- Baccilus or Rod
o Short rod called Coccobacillus (e.g. Serratia marcesecens)
| o Long rod called Spirochete or Spirillum (e.g. Treponema pallidum)
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- Spirillum
is a thick, rigid spiral
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- Spirochete
is a thin, flexible spiral
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- Vibrio
is a curved or comma-shaped rod
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Bacterial Size
- Cocci – 0.5 to 3 micrometer
- Bacilli – 0.2 to 2 micrometer in diameter and 0.5 to 20 micrometer in length
o Short bacilli – 0.2 to 2 micrometer
o Long bacilli – 0.5 to 50 micrometer
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- Cocci could be:
```
o Single
o Paired (diplococcus)
o Tetrad
o Cluster
o Chain
```
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- Bacillus could be
o Single
o Paired
o Chain
o Palisades
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- An endospore
dormant, highly resistant part of cell to preserve the cell’s genetic material in times of extreme stress.
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- The endospore consists of the bacterium’s
DNA, ribosomes and large amounts of calcium dipicolinate
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- Calcium dipicolinate is
a spore-specific chemical that appears to help in the ability for endospores to maintain dormancy (removes water)
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- Endospore is unique cellular structure.
o The outer coat surrounding the spore provides much of the chemical and enzymatic resistance.
o Next layer is cortex, it is a very thick layer of specialized peptidoglycan. It is needed for dehydration of the spore core, which aids in resistance to high temperature.
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- A germ cell wall resides under the
cortex (peptidoglycan).
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- The inner plasma membrane,
under the germ cell wall, is a major permeability barrier against several potentially damaging chemicals.
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- The center of the endospore, the core, exists in a very dehydrated state and houses the cells:
o DNA
o Ribosomes
o Large amounts of calcium dipicolinate
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- Endospores can be formed in
Gram positive bacilli only (Bacillus and Clostridium)
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- The types of position of endospore are:
```
o Terminal (e.g. Clostridium tetani)
o Central (e.g. Bacillus cereus)
o Subterminal (e.g. Bacillus Subtilis)
```
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- Terminal endospores are seen
at the poles of cells
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- Central endospores
more or less in the middle
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- Subterminal endospores
those between these two extremes, not to be considered either terminal or central
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- Lateral endospores are seen
occasionally
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- Prokaryotic cells reproduce by:
o Binary fission (a.k.a. transverse fission)
| o Budding
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- Bacteria are prokaryotic organisms that reproduce
asexually , most commonly by binary fission
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- In binary fission
the chromosomes duplicate and the cytoplasm splits into equal halves, i.e. binary fission results in the formation of two bacterial cells that are genetically identical
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Budding
– is a process in which a small protuberance develops at one end of the cell
o The protuberance enlarges and eventually develops into a new cell that separates from the parent cell
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- Bacterial growth in non-visible size
bacteria are so small that its growth in size cannot be measured
124
- Bacteria Growth is in the number
bacterial growth is measured by how many there are in the population, not how big each individual is
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Generation
```
is doubling process when the population increases by a factor of 2.
o 1 cell – 0 generations
o 2 cells – 1st generation
o 4 cells – 2nd generation
o 8 cells – 3rd generation etc.
```
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- Generation time or Doubling time
is the time required for a complete fission cycle from parent cell to two daughter cells
127
- Each bacteria has its specific doubling time.
o Staphylococcus – 30 minutes
o Streptococcus – 20 minutes
o E. coli – 17 minutes
128
- Bacterial growth needs
some nutrients, specific temperature, pH, moisture
129
- The most common component of the Petri plate
AGAR
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- Agar is a
complex polysaccharide, and it cannot be digested by bacteria. In room temperature it is solid.
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Growth Curve
1. Lag phase
2. Exponential (log) growth phase
3. The stationary phase
4. Death phase
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- Lag phase
– duration about 5 hours.
o Cells are not yet multiplying to maximum rate (amount of bacteria is constant)
o Bacteria are increasing their size to get read to divide
o It is also now as latent time
133
- Exponential (log) growth phase
phase – duration about 5-16 hours.
o Growth phase depends on proper pH, temperature and moisture
o This phase will continue as long as cells have adequate nutrients and environmental favorability
o Cells are dividing rapidly
o Patient begins to feel uncomfortable and the first clinical manifestations occur
134
- The stationary phase
– duration about 16-33 hours.
o Caused by less optimal conditions, the nutrients are limited
o Due to a decrease of nutrients the half of bacteria will eat and divide, and the other half will starve and die (the population of bacteria relatively constant)
o This is marked by declining of bacterial growth rate and an increase of their death rate
o Patient demonstrates an overt clinical manifestations of infection
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- Death phase
o The nutrients are depleted to the point where none of bacteria has food, and they all begin to die
o Rapid death occurs depending on the resistance of species
o This phase is slower than the exponential phase
o Patient starts to feel better
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Control of microbial growth”:
inhibits or prevents growth of microorganisms in two basic ways:
o By killing microorganisms (Microbiocidal agents)
o By inhibiting the growth of microorganisms (Microbiostatic agents)
137
Sterilization
```
- Is the complete elimination of all microbiological organisms to achieve aseptic, a sterile microbial environment. There are no degrees of sterilization: an object or substance is either sterile or not.
o Heat
o Radiation
o Chemicals
o Physical removal of cells
```
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- Heat – is the most important and widely used. It depends on:
The type of heat
| Time of application and temperature most importantly, to ensure destruction of microorganisms
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o Types of heat:
Incineration
| boiling
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Incineration
burns organisms and physically destroys them. Used for needles.
141
Boiling
100°C for 30 minutes. Kills everything except some endospores.
• Killing of endospores requires very long boiling (>6 hours)
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- Autoclaving
using steam under pressure as the sterilizing agent
– the most effective and most efficient means of sterilization
o Higher temperatures ensure more rapid killing.
o The usual standard temperature/pressure employed is 121°C/15 psi (pound per square inch) for 15 minutes.
o Moist heat is thought to kill microorganisms by causing denaturation of essential proteins
143
- Dry heat oven – is basically the cooking oven
o The dry heat is not as effective as moist heat (i.e., higher temperatures are needed for longer periods of time)
For example: 160°C/2 hours or 170°C/1 hour is necessary for sterilization
o The dry heat oven is used for glassware, metal, and objects that won’t melt.
144
- Irradiation:
usually destroys or distorts nucleic acids.
- UV Light
- x-rays, gamma radiation
- Electron beam radiation
145
o Ultraviolet light (commonly)
inhibiting DNA replication
146
o X-rays, gamma radiation highly
highly effective in killing microorganisms, break chemical bonds by interacting with the electrons of atomic constituents
147
o Electron beam radiation
alters various chemical and molecular bonds on contact
In living cells, these disruptions result in damage to the DNA and other cellular structures at the molecular level, cause the death of the organism or incapable of reproduction.
148
- Filtration
involves the physical removal of all cells in a liquid or gas
```
-important for sterilization of solutions which would be denatured by heat (e.g. antibiotics, injectable drugs, amino acids, vitamins, etc.)
o Chemical and gas:
Ethylene oxide
Formaldehyde
Ozone
Hydrogen peroxide
```
149
Control of Microbial Growth by Non Sterilizing Methods
- Heat
- Pasteurization
- low temp
- drying
- irradiation
150
Non ster.
| - Heat:
o Boiling 100° for 30 minutes – kills everything except some endospores, it also inactivates viruses.
For the purposes of purifying drinking water:
• 100°C for five minutes is a “standard”
151
- Pasteurization
the use of mild heat to reduce the number of microorganisms in a product or food
o For pasteurization of milk two methods are used;
Batch method: 63°C/30 minutes
Flash method: 71°C/15 seconds
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- Low temperature:
store perishable foods at low temperatures (4°C or less):
o To slow down the rate of bacterial growth
o To prevent production of toxins by bacteria
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- Drying
```
(removal of H2O): methods involve:
o Removal of water from product by heat
o Evaporation
o Freeze-drying
o Addition of salt or sugar
```
154
Non-steril.
| - Irradiation
(microwave, UV, x-ray): destroys microorganisms as described under “sterilization”
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Antimicrobial agents are chemicals that:
- Kill microorganisms (Microbiocidals) or
| - Inhibit the growth of microorganisms (Microbiostatics)
156
1. Antiseptics
microbiocidal agents, which are applied to living tissue and help reduce infection.
- They harmless enough to be applied to the skin and mucous membrane
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2. Disinfectants
antimicrobial agents that are applied to non-living objects to destroy microorganisms that are living on the objects
- Disinfection does not necessarily kill all bacteria, especially resistant bacterial spores, and some viruses. Examples:
o Alcohols
o Aldehydes (e.g. formaldehyde)
o Oxidizing agents (e.g. chlorine)
158
3. Antibiotics
antimicrobial agents produced by microorganisms that kill or inhibit other microorganisms. Examples:
- Penicillin (cell wall)
- Cephalosporin (cell wall)
- Polymyxin (cell membrane)
- Erythromycin (protein synthesis)
- Rifamycins (nucleic acid)
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Metabolism
1. Anabolism or biosynthesis:
| 2. Catabolism or biodegradation
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1. Anabolism or biosynthesis
Any process that results in the synthesis of cells molecules or structures – forming larger molecule from smaller molecules. Usually this process takes energy.
a. DNA
b. RNA
c. proteins
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2. Catabolism or biodegradation:
breaking down of large molecules and producing energy.
a. For biosynthesis
b. Cell movement
c. transport of nutrients
162
- Enzyme
large biological molecules responsible for the thousands of metabolic processes that sustain life
163
Enzymes characterized by
o Facilitate reaction by lowering energy of activation
o Each enzyme acts specifically upon its substrate
o Enzymes speed up the rate of metabolic activity
164
Three types of metabolism:
1. Fermentation
2. Respiration
3. Photosynthesis
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Fermentation
The incomplete oxidation of glucose or other carbohydrates in the absence of oxygen (fermentative organisms are anaerobic)
166
- For fermentation some bacteria obtain metabolic energy by a
Substrate-level Phosphorylation
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- Substrate-level phosphorylation is
a type of metabolic reaction that results in the formation of adenosine triphosphate (ATP) or guanosine triphosphate (GTP)
168
Respiration
- The set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP) by oxidative phosphorylation
- Almost all aerobic organisms carry out oxidative phosphorylation for production of energy
169
Photosynthesis
- A process used by plants and other organisms to convert light energy, normally from the sun, into chemical energy that can be later released to fuel the organisms’ activities
- Photosynthesis: Metabolic energy obtained by Cyclic Phosphorylation (similar to respiration except that photochemical processes uses energy of light)
170
Genetics
- The study of genes, heredity, and variation in living organisms
o Organism
o Cellular
o Chromosome with genes
o Molecular
171
- Organismal
genetics observes the transmission and expression of genetic factors in the whole organism or cell
172
- Chromosomal
genetics examines the characteristics and actions of chromosomes
173
- Molecular
genetics deals with the biochemistry of gene function
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Genome
- The genetic material of an organism and includes both the genes and the non-coding sequences of the DNA/RNA
- total genetic materials of a cell
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Gene: Organism level
gene is the fundamental unit of heredity responsible for a given trait in an organism
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Gene:
| Cell level
site of the chromosome that provides information for a certain cell function
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Gene:
| Molecular level
: a certain segment of DNA that contains the necessary code to make a protein or RNA molecule
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- DNA
two polynucleotide strands combined into a double helix
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- The basic unit of DNA is a nucleotide composed of
o Deoxyribose sugar
o Phosphate
o Nitrogen base
180
- 46 chromosomes of humans consists of
3 billion nucleotides
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- Each deoxyribose sugar bonds covalently in a repeating pattern with
(one up, one bottom), and one base.
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- One of the bonds is to the number 5’ carbon on deoxyribose,
and other is 3’ carbon, which specifies the order and direction of each strand.
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antiparallel arrangement
- The two polynucleotide chains run in opposite directions
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- Chain has a direction (known as polarity)
5’- to 3’- from top to bottom
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- The nitrogen bases include:
PURINES-A,G
PYRIMIDINES-T,C
- Purines and pyrimidines attach by covalent bonds at the 1’ position of the sugar
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Adenine (A)
(A) [bonds to T with two H+ bonds]
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Guanine (G)
[bonds to C with three H+ bonds]
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o Pyrimidines
Thymine (T)
| Cytosine (C)
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- DNA replication requires the action of
30 enzymes
190
o DNA in eukaryotic cells is
linear
191
o DNA in bacteria is
round
192
- DNA replication involves four basic steps:
o Uncoiling
o Unzipping
o Biosynthesis of complimentary polynucleotide
o The new strands are zipped and coiled
193
semi-conservative replication
preserving DNA code and passing it on to the daughter cells (Eukaryotic Cells)
194
- DNA in bacteria is round
in order to replicate it needs an origin of replication which is called bacterial replicon.
- The strands begin to separate from the origin of replication
- It opens in both directions and is filled in with complimentary basis from behind
195
- DNA can be copied for two reasons:
o To make more DNA
| o To make proteins
196
DNA molecule requires..
participation of RNA for replication
197
o RNA
```
Single stranded
Weaker sugar (ribose)
Nitrogen bases:
• Adenine
• Guanine
• Cytosine
• Uracil
```
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o DNA
```
Double stranded
Durable sugar (deoxyribose)
Nitrogen bases:
• Adenine
• Guanine
• Cytosine
• Thymine
```
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three types of RNA:
mRNA
tRNA
rRNA
200
mRNA
messenger RNA. It carries a copy of the genetic code from DNA to the ribosomes which make the protein.
201
tRNA
transfer RNA. It translates the mRNA into amino acids for protein synthesis.
202
rRNA
ribosomal RNA – the area inside the ribosomes pulling in mRNA to where the protein is made.
203
- Protein synthesis is characterized by two major steps
Transcription
| Translation
204
Transcription
the first step of protein synthesis when the information is transcribed from DNA to mRNA. Code of DNA is copied onto an RNA molecule (a messenger), like photocopy.
o The mRNA’s job is to carry information out of the nucleus to ribosomes.
205
Translation
tRNA arrives into ribosomes
rRNA pulls the mRNA to ribosomes safely
tRNA picks up an amino acid
tRNA delivers the amino acid to ribosomes
the amino acids are assembled into polypeptide proteins
206
A major form of gene regulation of protein synthesis and metabolism in bacteria is through systems called
operons
207
operon
is a section of DNA that contains one or more structural genes along with a corresponding operator gene that controls transcription
208
two different operons:
Inducible
| Repressible
209
- Inducible operons are
catabolic:
these operons are normally in the off mode.
-They are turned on by an enzyme's substrate for which the structural genes code. In this way, the enzymes needed to metabolize a nutrient (e.g. lactose) are only produced when this nutrient is present.
-
210
repressible operons
regulators of anabolic protein synthesis.
They contain genes coding for anabolic enzymes used to synthesize amino acids. This operon is normally in the on mode and will be turned off only when its amino acids are no longer required.
211
What does the lactose operon do?
It is an inducible operon which controls the catabolism and the transport of lactose in some enteric bacteria.
It is normally in an off mode and does not initiate enzyme synthesis when lactose is not present.
212
What are the three important segments found in the lactose operon?
Regulator
Control Locus
Structural Locus
213
What is important about the regulator segment found in the lactose operon?
It is composed of one gene that codes for a repressor.
| A repressor is a protein capable of repressing the operon.
214
What is important about the control locus in a lactose operon?
It is composed of two genes:
The promotor recognized by RNA
The operator which acts as an on/off switch for transcription
215
What is important about the structural locus?
It is made of three genes, each coding for a different enzyme.
Beta-galactosidase - hydrolyses the lactose into monosaccharides
Permease - brings lactose across the cell membrane
216
What does the repressible operon do?
It controls anabolism or biosynthesis.
This is the part of metabolism which builds large molecules.
The repressible operon synthesizes amino acids, purines, and pyrimidines in bacteria.
This operon is normally in the on mode and will be turned off when its nutrients are no longer required.
217
What is mutation?
It is any permanent, inheritable change in genetic information in a cell.
It is associated with an alteration in the nitrogenous base sequence in DNA
218
What is a wild type or a wild strain?
It is a microorganism that exhibits a natural, non-mutated characteristic.
219
What is a mutant strain?
It is a microorganism that bears a mutation.
220
What are the two different causes of mutation?
1. Spontaneous mutation
| 2. Induced mutation
221
spontaneous mutation?
a random change in DNA.
| It arises from errors in replication which occur without a known cause.
222
induced mutation?
results from exposure to known mutagens.
| Mutagens are primarily physical or chemical agents that damage DNA and its function (e.g. chemicals, radiation).
223
What are the two classifications of mutations?
1. Small-scale mutations
| 2. Large-scale mutations
224
What are small-scale mutations?
They affect a small gene in one or a few nucleotides.
225
What are the different small-scale mutations?
Point mutations - This mutation exchanges a single nucleotide for another. Point mutations are often caused by chemicals or malfunctions in DNA replication.
Insertions - This mutation adds one or more extra nucleotides into the DNA.
Deletions - This mutation removes one or more nucleotides from the DNA.
226
What are the different types of large-scale mutations?
Amplifications - This mutation involves duplicating all of the chromosomal regions, thus increasing the dosage of the genes within them.
Deletions - This mutation removes large chromosomal regions and the genes within those regions.
Chromosomal Translocations
Chromosomal Inversions
227
What are point mutations?
They are mutations which involve addition, deletion, or substitutions of single bases on a gene.
In other words, they are not large genetic sequences but just a single base nucleotide that is being altered.
228
What are the different point mutation types?
1. Missense mutation
2. Nonsense mutation
3. Silent mutation
4. Back mutation
229
What is a codon?
It is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid.
230
What is a missense mutation?
It is a mutation in gene code that changes a single nucleotide, resulting in a codon that codes for a different amino acid.
(She wrote "that leads to placement of different amino acids.")
It can:
Create a faulty, nonfunctional (or less functional) protein
Produce a protein that functions in a different manner
Cause no significant alteration in protein function
231
What is a nonsense mutation?
It is mutation which turns a normal codon into a stop codon. This will stop the production of the protein.
These mutations always create a nonfunctional protein.
232
What is a silent mutation?
What is a silent mutation? It is a mutation which alters a base but does not change the amino acid and, therefore, has no effect on the protein.
233
What is a back mutation?
It is a mutation in which a gene that has previously undergone a mutation reverses back into its original base composition.
234
Do cells have a system for finding and repairing DNA that has been damaged by various mutagens?
Yes. Most ordinary DNA damage is resolved by enzymatic systems specialized for such defects.
Mutations can be excised by a number of enzymes which remove the incorrect base and add the correct one.
235
How does mutation repair occur?
First, enzymes break the bonds between the base and sugar phosphate strand at the site of the error.
Second, a different enzyme removes the defective bases one at a time, leaving a gap that will be filled in by DNA polymerase.
236
How many proteins need to be altered to create a disease in a human being?
Only one (for example, sickle cell anemia)
237
What are the possible positive effects of mutation?
For microbial mutation, certain microorganisms bearing a protective mutation can adapt to a new environment.
238
What is genetic recombination?
It is a mechanism which bacteria have developed to increase their capacity for adaptation.
239
What happens during genetic recombination?
A bacterium donates DNA to another bacterium (intermicrobial transfer).
This results in a new strain different from both bacteria.
240
How is genetic recombination different from spontaneous mutation?
The genetic exchanges are usually beneficial to bacteria in genetic recombination.
It provides additional genes for resistance against:
Drugs and Poisons.
It also provides new nutritional and metabolic capabilities.
241
What are plasmids?
They are small, circular pieces of DNA that contain their own origin of replication and, therefore, can replicate independently of the bacterial chromosome.
242
Where are plasmids found?
They are found in the protoplasm (extrachromosomal DNA).
243
What are the three mechanisms for gene transfer?
Conjugation (bacterial sex)
Transduction
Transformation
244
What is conjugation?
It is a mode of genetic recombination in which a plasmid (fertility factor or F-factor) or fragment of DNA is transferred from a donor cell to a recipient cell via a direct connection (a pilus).
245
What is transduction?
It is a mode of genetic recombination in which the bacterial transfer is mediated through a virus.
246
What happens during transduction?
```
A virus (a bacteriophage, specifically), takes a gene from one bacterial cell and carries it to other bacterial cells.
Thus, two bacteria are not attached.
```
247
What is transformation?
It is the transfer of naked DNA that requires no special vehicle.
248
How is transformation distinct from transduction and conjugation?
Whereas transduction and conjugation require two living cells, transformation does not.
249
What happens during transformation?
The gene from dead bacteria can be transferred into a live bacterium. This makes it more virulent.
This usually happens in a genetic engineering laboratory.
250
What is genetic engineering?
It is the process of manually adding new DNA or a gene to an organism.
It is also called transformation.
251
How does genetic engineering work?
It works by physically removing a gene from one organism and inserting it into another, giving it the ability to express the traits encoded by that gene.
252
In terms of genetic engineering, what can happen to a specific DNA fragment?
It can be isolated, amplified, and/or expressed at high levels.
253
What are the ways in which DNA fragments are manipulated in genetic engineering?
Preparation of DNA fragments
Separation of DNA fragments
Cloning of DNA restriction fragments
254
What happens during the preparation of DNA fragments?
The DNA is removed and cut by an endonuclease enzyme (a.k.a. a restriction enzyme) into pieces.
255
How does the endonuclease enzyme cut the DNA?
It cuts the DNA at a specific site.
256
What do the restriction enzymes do?
They incise the DNA through each sugar-phosphate backbone (i.e. each strand).
As a result, the cuts have a sticky end.
257
What happens during the separation of DNA fragments?
Gel electrophoresis is used to separate the DNA fragments according to length. This is the basis of size (molecular weight) of the fragment.
258
What happens during gel electrophoresis?
Pieces of DNA are moved through the gel by a small current.
The longer, heavier DNA fragments move slower than the shorter, lighter ones.
The longer, heavier fragments will be on top of the gel.
The shorter, lighter fragments will move faster and will be on the bottom of the gel.
259
What does ethidium bromide do during the separation of DNA fragments?
It binds to the DNA fragments and forms a bright, fluorescent [something] (I wrote down "adduct," but it can't be that...).
This gives one the ability to see the DNA fragments in the gel.
260
How do you clone DNA restriction fragments?
Polymerase chain reaction (PCR) is a molecular copy machine for DNA.
261
How does polymerase chain reaction (PCR) copy DNA?
It is inserted into bacteria and transforms bacteria into a new bacteria with a new gene.
The manipulation of bacterial DNA generally occurs within a plasmid.
262
What are the various environmental factors which can influence microbes?
```
Temperature
Gas
pH
Radiation
Osmotic Pressure
Moisture
Nutrient Content
Competitive Microflora
Biological Structure
```
263
Is there an optimum growth temperature for bacteria?
Yes, but it varies.
| Bacteria in the human gut grows well at body temperature, but plant bacteria may be killed at that temperature.
264
What is optimum temperature?
It is the temperature at which the bacterium grows most rapidly. Metabolism is at its maximum level at this temperature.
265
What is minimum temperature?
It is the lowest temperature that permits bacterial growth. The metabolism functions at a low rate. Below this temperature, no growth occurs.
266
What is maximum temperature?
It is the highest temperature at which growth and metabolism can occur.
If it rises slightly above this temperature, the maximum growth will stop.
Any further rise in the temperature will inactivate enzymes and nucleic acids, then cell death will occur.
267
What are psychrophilic bacteria?
They are cold loving bacteria. They are commonly found in refrigerators.
The optimum temperature for psychrophilic bacteria is at temperatures below 15 - 20 degrees Celsius.
Their minimum temperature is at 0 degrees Celsius (32 degrees Fahrenheit).
268
What leads to a build up of psychrophiles?
Improperly packaged foods (raw meat, milk, fish, poultry, eggs)
Improper sanitation in the refrigerator
Inappropriate refrigerator temperature
269
What are some of the harmful health conditions produced by exposure to psychrophilic bacteria?
```
Sepsis
Food Poisoning
Gastrointestinal infections
Meningitis
Urinary tract infections
```
270
What are some examples of different psychrophilic bacteria?
Vibrio
Pseudomonas
Listeria
271
What does mesophilic mean?
Middle loving
272
What is the optimum temperature for mesophilic bacteria?
It is at 20-40 degrees Celsius (70-90 degrees Fahrenheit).
|
273
What kind of bacteria is mesophilic bacteria?
It is a human type of bacteria (beneficial, opportunistic, or pathogenic).
Its peak reproduction and activity is between 30-37 degrees Celsius (86-99 Fahrenheit).
Pathogenic bacteria can grow at 30-40 degrees Celsius and is also involved in food contamination and degradation (like bread, grains, meats, etc).
274
Which are the most common bacterial infections in humans?
They are mostly caused by mesophilic bacteria that find their optimal growth temperature at around 36 degrees Celsius (98.6 degrees Fahrenheit) - normal human body temperature.
275
What are some examples of pathogenic mesophiles?
```
Pseudomonas maltophilia
Streptococcus pyogenes
Escherichia coli
Staphylococcus aureus
Streptococcus pneumoniae
Clostridium
```
276
What are some examples of beneficial, mesophilic bacteria found in human intestines?
Lactobacillus acidophilus
| Bifidobacterium
277
What are thermoduric bacteria?
They are bacteria which can survive, to varying extents, the pasteurization process (temperatures above 40 degrees Celsius).
These include bacillus and clostridium (which are normally mesophiles).
278
What are thermophilic bacteria?
They are heat loving bacteria.
| Their optimum temperature is at 50-60 degrees Celsius.
279
What are some of the issues created by thermophilic bacteria?
They are problematic for pasteurizing milk, because they grow at high temperatures.
Some can cause canned foods to spoil, because they produce highly resistant spores.
280
What are the three atmospheric gases which have the most influence on microbial growth?
Oxygen
Carbon Dioxide
Nitrogen
281
What are the two types of bacteria influenced by the presence or absence of oxygen?
1. Aerobic - Microaerophyle
| 2. Anaerobic - Facultative Anaerobic Aerotolerant
282
What are obligate aerobic bacteria?
They are microorganisms that grow well in the presence of normal atmospheric oxygen.
283
What do obligate aerobic bacteria use oxygen for?
To metabolize substances, like sugars or fats, to obtain energy and create enzymes (catalase / peroxidase, dismutase) needed to process toxic products.
For example:
Normally, H2O2 kills bacteria, but some bacteria can break it down.
Reaction 1 enzyme dismutase = 2O2 + H+ = H2O2 + O2
Reaction 2 enzymes 2H2O2 ----> 2H2O + O2 (via catalase or peroxidase)
284
What is a microaerophile?
It is a microorganism that needs oxygen, but it also needs environments containing lower levels of oxygen than are present in the atmosphere.
Many also require an elevated concentration of carbon dioxide.
285
What is an example of a microaerophile?
```
Helicobacter pylori (we need to know this name)
It is a gram negative bacili which may live in the stomach's low pH.
80% of stomach/duodenum ulcerations are caused by this bacteria.
```
286
What are some examples of aerobic bacteria?
```
Staphylococcus species
Streptococcus species
Bacillus cereuce
Enterobacteriacae species
Pseudomonas aeruginosa
Mycobacterium tuberculosis
```
287
What are the three different types of anaerobic bacteria?
Obligate anaerobes
Facultative anaerobes
Aerotolerant bacteria
288
What are obligate anaerobes?
They are microorganisms that are killed by normal atmospheric concentrations of oxygen - 21% of O2.
They need environments without any oxygen.
H2O2 kills them.
289
What are facultative anaerobes?
They can grow with or without oxygen, because they can metabolize energy aerobically or anaerobically.
290
What are aerotolerant bacteria?
They do not need oxygen to grow, but can survive in the presence of oxygen.
291
What are some examples of anaerobic bacteria?
Clostridium tetani (which causes tetanus)
Clostridium botulinum (which causes food poisoning)
Escherichia coli
Klebsiella pneumoniae (enterobacter)
Listeria
Salmonella
292
Which pH level is comfortable for most bacterial growth?
6-8 pH
293
What are acid loving microbes called?
Acidophiles, they can thrive in acidic conditions at as low as 1, 2-4 pH.
294
What is an example of an acidophile?
Helicobacter pylori
They are gram negative bacillus, non-spore forming, lives in stomach mucous at a pH of 2-4.
H. pylori produces high amount of urease.
Urease is an enzyme that degrades urea, and by doing so decreases the acidity of the stomach, resulting in:
Chronic gastritis, peptic ulceration, adenocarcinoma
295
What is an example of a bacterium which can grow at pH levels of 8-9?
Vibrio cholerae - a gram negative bacillus, comma-shaped bacterium, creates the disease cholera, facultative anaerobic bacterium
296
What are the various interactions a microorganism can have and between what?
Their interactions can be: beneficial, neutral, or harmful.
| They interact with: microbes, multicellular organisms, and viruses.
297
What are different examples of symbiotic relationships?
Mutualism, Commensalism, and Parasitism
298
What are some examples of non-symbiotic relationships?
Synergism and Antagonism
299
What is symbiosis?
It is a close and often long-term interaction between two or more different biological species.
They include associations in which on organism lives on or inside (endosymbiosis) another organism.
An example of endosymbiosis is lactobacilli in the human body.
300
What are obligate symbiotic relationships?
Both symbiotes entirely depend on each other for survival.
| For example, many lichens (consisting of fungus) cannot live on their own.
301
What are facultative symbiotic relationships?
They can, but do not have to, live with the other organism.
302
What is mutualism?
Both bacteria and their host benefit from each other.
For example, there are several kinds of bacteria which live inside the mouth, nose, throat, and intestines of humans and animals.
These bacteria receive a place to live and feed while keeping other harmful microbes from taking up residence.
303
What is an example where we need mutualist relationships with bacteria?
We need human gut flora to digest food efficiently and synthesize vitamins like vitamins K and B.
304
What is commensalism?
One organism benefits without affecting the other.
| One organism utilizes a substrate and forms a product that can be used by another organism.
305
What is an example of commensalism?
Microflora living on our skin benefit from us, but we do not necessarily benefit from them.
306
What is parasitism?
The bacteria benefit while the host is harmed.
Pathogenic parasites, which cause disease, do so by resisting the host's defenses and growing at the expense of the host.
307
What do parasitic bacteria produce?
Poisonous substances called endotoxins and/or exotoxins which are responsible for the symptoms that occur with an illness.
308
What are some examples of commensalism type bacteria?
Corynebacterium species
| Mycobacterium species
309
What is an example of a mutualism type bacteria?
E. coli species in the large intestine
310
What is synergism?
It is a cooperative relationship between organisms that is beneficial for both members but not obligatory for either.
311
- Symbiotic:
o Mutualism
o Commensalism
o Parasitism
312
- Nonsymbiotic:
o Synergism
| o Antagonism
313
What are normal flora?
```
They are bacteria which are found in or on our bodies on a semi-permanent basis without causing disease.
Star this term
You can study starred terms together
```
314
What aspects of our body are constantly in contact with environmental organisms and become readily colonized by various microbial species?
Our surface tissues, i.e., skin and mucous membranes
315
What's normally free of microorganisms?
Blood, meninges, brain, abdominal cavity, and muscle
|
316
About how many bacteria live in our bodies?
Around 10^14 bacteria
317
What are the various ways in which normal flora protects us from disease?
1. Competing with invading bacteria for space and nutrients
2. Producing compounds which kill other bacteria
3. Lowering the pH so that other bacteria cannot grow
4. Produce vitamins we are unable to produce like vitamins B3 and K
5. Boosts the development of our immune system
6. Help us digest food
318
What can happen if normal flora escapes from their normal location to other locations?
They can cause disease.
For example, Escherichia coli, commonly found in the intestine, can cause urinary tract infections if introduced into the bladder or kidney.
319
What can immunosuppresion cause?
It can allow otherwise harmless bacteria to cause disease.
AIDS, cancer treatments, and transplant rejection drugs all suppress the immune system and occasionally allow the normal flora to create serious diseases.
320
What is infection?
It is the invasion and multiplication of microorganisms such as bacteria, viruses, and parasites that are not normally present within the body.
An infection may cause no symptoms and be subclinical, or it may cause symptoms and be clinically apparent.
321
Where can an infection occur?
It can remain localized or spread through the blood and lymphatic vessels to become systemic (bodywide).
322
What is disease?
It is a particular abnormal, pathological condition that affects part or all of an organism.
It is often construed as a medical condition associated with specific symptoms and signs.
323
What can cause disease?
By factors originally from an external source, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune diseases.
324
What is a contaminant?
A contaminant is a biological, chemical, physical, or radiological substance (normally absent in the environment) which, in sufficient concentration, can adversely affect living organisms through air, water, soil, and/or food.
325
What is morbidity?
Morbidity (from the latin morbidus, meaning "sick, unhealthy") is a diseased state, disability, or poor health due to any disease.
The term may be used to refer to the existence of any form of disease or to the degree that the health condition affects the patient.
326
What is mortality?
It is the number of deaths that occur at a particular time or place.
327
What are the various actions of pathogenic microbes on tissue?
Contact - microbes adhere to exposed body surfaces.
Invasion - microbes cross lines of defense and enter sterile human cells and tissue.
Infections - pathogenic microorganisms have become established in the tissues of the host organism and multiply throughout the tissues
328
What are the sites that harbor normal flora?
```
Skin
Upper Respiratory Tract
Alimentary Tract (GI tract)
Lower Urinary Tract (Urethra)
External Genitalia
External Ear Canal
External Eye (Eyelid, Conjunctiva)
```
329
Which area of the body has the most diverse and abundant flora?
In the mouth!
There are hundreds or more different bacteria.
Cheek epithelium, tongue, floor of the mouth, and teeth predominantly have aerobic streptococci.
330
Which bacteria are major contributors to dental cavities?
Streptococcus mutans and Streptococcus sanguis.
These two bacteria are cariogenic microorganisms that break down sugar for energy and produce an acidic environment, which demineralizes the superficial structure of the tooth.
The result of the conversion disintegrates the coating of the tooth and then later dissolves the calcium molecule, creating a hole.
331
How long does it take for the newborn's sterile mouth to become a home to streptococcal species?
Within about 2 days, predominantly Streptococcus mitis and Streptococcus salviarius, will establish themselves in the mouth and predominate the area during the first year of a newborn's life.
They will account for roughly 70% of the total flora.
332
What is a general outline of the process of infection?
Microbes enter the body.
They cross the host barrier (innate and acquired immunity).
They multiply in the target tissues.
As they multiply, they produce toxins and enzymes, causing infection.
They then release to the exterior world. Upon getting out of the body, they can then get into another individual and infect all over again
333
What is the portal of entry?
It is the initiation of infection
334
What are portals of entry?
They are the same as anatomical sites for normal flora.
For example, skin, alimentary, respiratory, and urogenital tracts are all portals of entry.
Not all bacteria enter from the same site. They will have one or two specific portals of entry.
For example, with Cholera vibrio:
-alimentary tract inoculation results in infection
-skin inoculation does not result in infection
335
What is an infectious dose (ID)?
It is the minimal number of microorganisms required to initiate an infection.
336
What does an infectious dose vary according to?
The pathogenic agent
The consumer's age
Overall health
337
What is pathogenicity?
It is the potential capacity of certain species of microbes or viruses to cause disease.
338
What is virulence?
It is the degree of pathogenicity within a group or species of parasites as indicated by:
case fatality rates
and/or
the ability of the organism to invade the tissues of the host.
339
What is pathogenicity determined by?
It is determined by its virulence factors.
|
340
What is a virulence factor?
Is is a property which contributes to a pathogen's capacity to infect host tissues.
```
Some virulence factors include:
The number of infecting bacteria
The route of entry into the body
The effects of host defense mechanisms
Intrinsic characteristics of the bacteria
```
341
What are pathogenic microbes (primary pathogens)?
They are the pathogens that are capable of infection and disease in healthy people with normal immune defenses.
342
What are opportunistic pathogens (secondary pathogens)?
They can only infect people who have had their host defenses (immunity) compromised.
343
What are some factors that increase the risk of opportunistic virulence?
```
Old Age
Being an Infant
Malnutrition
Genetic Defect(s) in Immunity
Acquired Immunity Deficiency (a.k.a. AIDS)
Cancer
Chemotherapy, radiotherapy, etc
```
344
What the three steps in invasion and tissue damage?
Attachment
Colonization
Invasion
345
What is attachment?
It is characterized by adhesion.
| Adhesion is a process by which many bacteria must first bind to host cell surfaces.
346
What's responsible for adhesion?
Bacteria - pilli, fimbriae, capsule, and adhesive slime
Virus - specialized receptors
Protozoa - organelle of locomotion
Parasitic worm - suckers and hooks
347
What is colonization?
It is a process when virulent bacteria produce special proteins that allow them to colonize parts of the host body.
For example, Helicobacter pylori is able to survive in acidic environments like the human stomach by producing the enzyme urease.
348
What is invasion?
It is a process when virulent bacteria produce proteins that disrupt host cell membranes.
Virulence factors allow bacteria to enter host cells and facilitate entry into the body across epithelial tissue layers at the body surface.
349
What are the common virulence factors for bacteria?
Proteins or other molecules that are synthesized by enzymes.
| Genes in chromosomal DNA or plasmids contain the code for these proteins.
350
What do exoenzymes (a.k.a. extracellular enzymes) do?
They dissolve the host defense barrier and promote the spread of microbes to deeper tissues.
```
Some exoenzymes include:
Mucinase
Keratinase
Collagenase
Hyluroindiase
Coagulase
Bacterial Kinase
Nuclease
```
351
What does mucinase do?
It digests mucous membranes.
| Vibrio cholera produces this.
352
What does keratinase do?
It digests the components of skin and hair.
| Fungi produces this.
353
What does collagenase do?
It digests fibers in connective tissue.
| Clostridium produces this.
354
What does hyaluranidase do?
It is a spreading factor which digests ground substances that cement cells together.
Staphylococcus, Streptococcus, and Clostridium produce this.
355
What does coagulase do?
It clots blood.
| Staphylococcus produces this.
356
What does bacterial kinase do?
It causes fibrin clots to dissolve.
Streptococcus produces streptokinase.
Staphylococcus produces staphylokinase.
357
What does nuclease do?
"causes distraction of nucleic base of DNA."
Wikipedia says, "A nuclease is an enzyme capable of cleaving the phosphodiester bonds between the nucleotide subunits of nucleic acids."
Staphyloccocus aureus and Corynebacterium diphtheriae produce this.
358
What are toxins?
They are specific chemical products produced by microbes, plants, and animals that are poisonous to other living things.
359
What is toxogenicity?
It is the ability to produce toxins.
360
What is toxemia?
It is the spread of a toxin through the blood.
|
361
How do we classify toxins?
They are classified based on the ways in which they are produced.
362
What is an exotoxin?
It is a toxin secreted by living bacterial cells.
The toxin is secreted outside of the cell.
These are produced by both Gram positive and Gram negative bacteria.
363
What is an endotoxin?
It is a part of the structure of bacteria.
It is not released until the bacterium has died.
These are only produced by Gram negative bacteria.
364
Where are exotoxins synthesized?
In the cytoplasm. They may or may not be secreted.
|
365
What are exotoxins made of?
Protein
366
Exotoxins are heat-labile (unstable). What does this mean?
They can be destroyed at 60 degrees Celsius.
367
Which is more toxic, an exotoxin or an endotoxin?
Exotoxins are more toxic.
| They are made to attack specific target cells.
368
What do exotoxins stimulate the production of?
Antitoxins by the immune system
369
Can exotoxins create a fever in the host?
No.
370
What are the different types of exotoxins, and what do they do?
Neurotoxins - act on neurons
Enterotoxins - act on intestinal tract
Hemotoxins - lyse red blood cells
Nephrotoxins - damage kidney cells
371
How are endotoxins released?
By distraction, lysis, or dead bacteria.
372
What are endotoxins made of?
Lipopolysaccharides (LPS) from the outer part of the cell wall.
They consist of Lipid A
373
Are endotoxins heat-stable?
Yes, they can be destroyed at 100 degrees Celsius or higher.
374
Can endotoxins be converted into toxoids?
No. They also do not stimulate the creation of antitoxins.
375
What are the effects of endotoxins?
They have a general toxic effect on all cells of the body (a non-specific toxicity).
They can create a fever.
376
What are the two major antiphagocytosis factors in bacteria?
Leukocidine and the Capsule or Slime Layer
377
How does leukocidine prevent phagocytosis?
Bacteria secrete leukocidine.
It is toxic to white blood cells.
Streptococci and Staphylococci can produce leukocidine.
378
What are some bacteria which secrete a capsule or slime layer?
Streptococcus pneumonia and Salmonella typhi can secrete capsules.
Neisseria meningitides can secrete a slime layer.
379
What is latency?
It is when a microorganism goes into an inactive state.
380
What is recurrence?
It is when a microorganism activates and induces disease again.
For example, herpes simplex, syphilis, tuberculosis, and malaria can move from periods of latency to recurrence.
381
What are the three origins of pathogens?
Reservoir
Source
Carrier
382
What is a reservoir?
It is any person, animal, arthropod, plant, soil, or substance (or combination of these) in which an infectious agent normally lives and multiplies, on which it depends upon for survival, and where it reproduces itself in such a manner that it can be transmitted to a susceptible host.
383
What are some animate reservoirs?
People
Insects
Birds
Other animals
384
What are some inanimate reservoirs?
```
Soil
Water
Food
Feces
Intravenous fluid
Equipment
```
385
What is a source?
It is the immediate origin of an infectious agent.
386
What are the five different sources of pathogens?
```
Raw food
People
Pests and Pets
Soil
Dust and Dirt
```
387
What is a carrier?
It is an individual that spreads pathogens to others
|
388
What are the different types of carriers?
Asymptomatic carrier
Passive carrier
Chronic carrier
Convalescent carrier
389
What is an asymptomatic carrier?
A person or other organism that has contracted an infectious disease, but who does not display symptoms.
390
What is a passive carrier?
A healthy person whose body carries the causal organisms of an infectious disease, but they have not contracted the disease and do not display symptoms.
391
What is a chronic carrier?
It is an individual who acts as a host to pathogenic organisms for an extended period without displaying any signs of disease.
392
What is a convalescent carrier?
It is a person who has recovered from the symptoms of an infectious disease, but they are still capable of transmitting pathogens to others.
393
What is a portal of exit?
It is the site where microorganisms leave the host to enter another host.
394
How does a microbe leave the upper respiratory tract's portal of exit?
Saliva from the oral cavity
Sneezing
Coughing
395
How does a microbe leave the gastrointestinal tract's portal of exit?
Feces / diarrhea from the bowels
| Vomiting
396
What is the blood's portal of exit?
Infected blood
397
How does a microbe leave the urogenital tract's portal of ext?
Semen
Vaginal secretions
Infected urine
398
What is the skin and mucous membranes' portal of exit?
Discharges from infected skin lesions and infected wounds
|
399
What are nosocomial infections?
They are infections that have been caught in a hospital and are potentially caused by organisms that are resistant to antibiotics.
400
What does the word nosocomial mean?
The term "nosocomial" comes from two Greek words: "nosus" meaning "disease" and "komeion" meaning "to take care of."
Hence, "nosocomial" should apply to any disease contracted by a patient while under medical care.
401
What is the percentage of infectious diseases acquired during a stay at the hospital?
0.1-20%
The average is 5%
Gram negative rods (E. coli, Klebsiella, Pseudomonas) are most often cultured from patient specimens, followed by Staphylococci and Streptococci.
402
What's the history behind Koch's principles?
They were formulated by Robert Koch and Friedrich Loeffler in 1884.
They were based on earlier concepts described by Jakob Henle.
403
What are Koch's principles?
They are four criteria designed to establish a causative relationship between a microbe and a disease.
404
Koch's principles 1
The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
405
Koch's principles 2
2. The microorganism must be isolated from a diseased organism and grown in a pure culture.
406
Koch's principles 3
3. The cultured microorganism should cause disease when introduced into a healthy organism.
407
Koch's principles 4
4. The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
408
What are the stages in the course of infectious disease?
```
Incubation period
Prodromal Stage
Period of Invasion
Convalescent Period
Terminal Stage
```
409
What is the incubation period?
It is the time when an organism becomes infected with a microbe.
- There are no symptoms during this time.
- Incubation periods are different for different microorganisms.
410
What is the prodromal stage?
It is the time when the microbes begin to multiply, and the signs and symptoms begin to occur.
411
What is the period of invasion?
It is the period when the microbes are growing, and the signs and symptoms hit their zenith.
412
What is the convalescent period?
It is the time when the number of bacteria decreases and recovery begins.
413
What is the terminal stage?
It does not occur if there was a convalescent period.
| If, however, the organism could not recover, then the terminal stage begins and the body dies.
414
What are the patterns of infection?
```
Localized infection
Generalized or systemic infection
Focal infection
Mixed infection
Acute infection
Chronic infection
Subacute infection
```
415
What is localized infection?
The bacteria remain limited to one area of the body
416
What is generalized or systemic infection?
The bacterial infection enters the fluid (blood/lymph) and spreads to several areas.
417
What is a focal infection?
The bacterial infection spreads from one area to another area.
418
What is a mixed infection?
It is an infection by more than one type of microbe (two different bacteria or a bacteria and a virus, etc.).
419
What is an acute infection?
It is a severe infection that lasts a relatively short period of time.
420
What is a chronic infection?
Is is not a severe infection that lasts a long period of time. The severity, however, gradually increases.
421
What is a subacute infection?
It is an infection midway between acute and chronic.
|
422
What are the warning signals of disease?
Sign
Symptom
Syndrome
Blood signs
423
What is a sign?
Any measurable evidence of the infection which can be seen by an observer. In essence, it is an objective manifestation of a disease.
424
What is a symptom?
It is something that is felt or seen but cannot be measured. In essence, it is a subjective manifestation of a disease.
425
What are the different blood signs?
Leukocytosis - increased white blood cells
Leukopenia - decreased white blood cells
Septicemia (bacteremia) - blood is not sterile
Viremia - virus in the blo
426
What are the various kinds of epidemiology?
```
Prevalence
Incidence
Endemic
Sporadic
Epidemic
Pandemic
```
427
What is prevalence in epidemiology?
It is the total number of existing cases with respect to the entire population.
In essence, this is a ratio:
Total number of infected people / Total number of people
428
What is incidence in epidemiology?
It is a ratio concerning the number of new cases during a certain period of time over a healthy population.
429
What is endemic in epidemiology?
It is a constant number of cases during a long period of time in a specific geographic area.
430
What is sporadic in epidemiology?
It means a disease occurring occasionally, singly, or irregularly.
431
What is epidemic in epidemiology?
It means prevalence of cases increase unexpectedly.
|
432
What is pandemic in epidemiology?
It is the spread of an epidemic over a continent.
|
433
What is surveillance in epidemiology?
It is the rate of occurrence, mortality, morbidity, and transmission of infections.
