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Microbiology Quiz 1 > Microbio 3-18 structure function > Flashcards

Microbio 3-18 structure function Flashcards

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1
Q

What are two important bacteriological procedures?

A

sterilization & aseptic technique

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2
Q

What’s the difference between sterilization and aseptic technique?

A

Sterilization - preparation of media/instruments such that no living bacteria are present. Aseptic Technique: allows manipulation of sterilized material without bacteriological contamination

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3
Q

What is the first basis of classification for bacteria? What are two examples? How are they classified today?

A

shape. 1) cocci (round-shaped) and 2) bacilli (rod-shaped). They are now classified depending on the extent of DNA sequence homology

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4
Q

How do you identify a gram + from a gram - stain?

A

Gram + is violet; Gram - is red

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5
Q

What are the 4 most important bacterial characteristics?

A

1) morphology of colonies on appropriate agar medium. 2) microscopic morphology and staining of individual bacteria. 3) biochemical profiles (ability to ferment a particular sugar). 4) specific antigens detected by known anti-sera

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6
Q

What are Koch’s postulates? (4)

A

1) the MO must be PRESENT in all organisms suffering from the disease, but not in healthy organisms. 2) the MO must be isolated from a diseased organism and grown in pure culture. 3) the cultured MO should cause disease when introduced into a healthy organism. 4) the MO must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

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7
Q

Can Koch’s postulates be applied to all MO? Why/Why not?

A

No, not all infectious bacterium will fulfill Koch’s postulates (ie those that cannot grow on laboratory medium, but requir a host cell to grow)

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8
Q

What are Koch’s molecular postulates?

A

1) the phenotype under investigation should be ASSOCIATED significantly more often with a pathogenic organism than with a nonpathogenic member or strain 2) Specific INACTIVATION of a gene (or genes) associated with the suspected virulence trait should lead to a measurable derease in virulation 3) RESTORATION of full pathogenicity should accompany replacement of the mutated gene with the wild-type organism

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9
Q

Name whether Fungi, Protozoa, and Bacteria have pathogens, are photosynthetic, or if they have a rigid cell wall.

A

Fungi has some pathogens, non-photosynthetic, and has a rigid cell wall. Protozoa have some pathogens, no rigid cell wall, non-photosynthetic. Bacteria have many pathogens, require organic compounds as energy source (but some of the are photosynthetic), and all (but one) have a rigid cell wall.

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10
Q

MOs are divided into two sub-groups on the basis of the structure of the individual cell. What are they?

A

Prokaryotes and Eukaryotes

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11
Q

What are examples of eukaryotes? (3) What are examples of prokaryotes? (1)

A

E: fungi, protozoa, algae. P: bacteria

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12
Q

How do eukaryotes and prokaryotes differ in terms of their chromosomes and their segregation?

A

E: linear chromosomes contained within nuclear membrane (segregation involves mitosis) P: one circular chromosome not bound by a nuclear membrane (segregation does not involve mitosis)

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13
Q

How do eukaryotes and prokaryotes differ in terms of their sexual reproduction?

A

E: sexual reproduction occurs by meiosis P: reproduction occurs by partial, unidirectional transfer of DNA

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14
Q

How do eukaryotes and prokaryotes differ in terms of their membrane bound structures?

A

E: contains mitochondria that carries out oxidative phosphorylation. P: no mitochondria, but oxidative phosphorylation occurs at the cell membrane

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15
Q

How do eukaryotes and prokaryotes differ in terms of their mobility?

A

E: motbility accomplished by cytoplasmic streaming (amoeboid movement) or by contraction of flagella (microtubule 9 doublet x 2 singlet arragement surrounded by cell membrane) P: flagella (flagellin subunits forming a central hollow tube) are present in some bacteria and it is not surrounded by cell membrane

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16
Q

How do eukaryotes and prokaryotes differ in terms of their cell wall?

A

E: animal cells do NOT have cell walls. Higher plants/algae have cell walls that are comprised of CELLULOSE (glucose polymer). Fungi have cell walls that are comprised of CHITIN (acetyl glucosamine polymer) and B-1,3-GLUCAN. P: cell walls are comprised of PEPTIDOGLYCAN, which consists of N-ACETYL glucosamine (NAG) lined to MURAMIC ACID (acetyl glucosamine linked to lactic acid), D-AMINO ACIDS. and other UNUSUAL A.A.

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17
Q

Penicillin affects with what component of the prokaryotic cell?

A

it inteferes with the formation of the peptidoglycan (ie it interferes with the cross-linking between polymer chains)

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18
Q

What ribosomes are present in eukaryotes vs prokaryotes?

A

E: 80S, P: 70S (think: P’s are simpler and have a smaller ribosome)

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19
Q

Sterols are present in eukaryotic cells, but absent in prokaryotic cells. What is the one exception?

A

mycoplasma, which may contain sterols in their membrane.

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20
Q

In a clinical specmiens,how would you tell whether a cell is a bacteria or a cell from the host?

A

cells larger than 10µm are not bacteria

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21
Q

How do eukaryotes and prokaryotes differ in terms of their RNA/protein synthesis?

A

E: RNA is transcribed in the nucleus, spliced, and transported out to the ER, where it is transported into protein. P: nascent RNA is translated as it is transcribed and RNA splicing does NOT occur

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22
Q

Prokaryotes are subdivided into these two major groups:

A

bacteria (true bacteria) and archaea (which inhabit unusual environmental niches)

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23
Q

What are the general morphological types of bacteria?

A

1) cocci (spherical), 2) bacillus (rod shaped), 3) curved rod or spiral

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24
Q

How do most bacteria multiply?

A

binary fission

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25
What is binary fission?
form of asexual reproduction/cell division used by all prokaryotes, and some organelles within eukaryotic organisms (ie mitochondria). The single DNA molecule first replicates and each is then attached a different part of the cell membrane. A central tranvesere wall forms between the two daughter cells. When the cell begins to pull apart, the chromosomes are separated. Results in genetically identical cells
26
What are filaments and what type of bacterial cells are they most common in?
filaments are bacteria cell-aggregates that occur when the daughter cells do not separate after completion of the transverse wall
27
How are streptococci cells usually arranged?
chain of cocci
28
How are staphylococci cells usually arranged?
irregular clusters
29
How are aerobic bacilli cells usually arranged?
chains of rods (think hot dog links)
30
how are corynebacterium cells (causes diphtheria) usually arranged?
stacks of rods or a variety of groupings arranged in chinese-characters like orientations
31
What properties do the cell wall confer that a plasma membrane wouldn't?
Because of the strength and rigidity of its wall, large changes in the osmotic pressure of the environment have little effect on cell shape. Mammalian cells lack a cell wall and therefore its shape will change depending on the ionic strength of the surrounding medium
32
What are protoplasts?
a plant, bacterial or fungal cell that had its cell wall completely or partially removed using either mechanical or enzymatic means.
33
T/F Protoplasts are affected by osmotic changes
True. Since they lack a cell wall, the cell can burst or shrink depending on the osmotic strength of the media
34
What are the functions of the prokaryotic cell membrane? (3)
1) contains oxidative enzymes (cytochromes, quinones, ATPase) and resembles the inner membrane of the mitochondrial membrane. 2) contains enzymes that function in cell wall synthesis. 3) selective transport systems to deliver sugars, a.a., metals, etc and secreting toxins and certain enzymes.
35
What is the periplasmic space? What's in it? What type of bacteria is it found in? Where is it usually found?
located between the cytoplasmic membrane and outer cell wall; contains enzymes that degrade extracellular substances of high m.w. (ie amylase can degrade proteins or polysaccharides) and binding proteins. It is found in Gram - bacteria, between the inner and outer membranes
36
What is the medical importance of the periplasmic space?
it may contain enzymes that degrade antibiotics (confers antibiotic resistance)
37
Is periplasmic space found in gram + bacteria?
No
38
Gram - bacteria has their degradative enzymes in their periplasmic space. Where do gram + bacteria keep theirs?
Since there is no periplasmic space in the gram + bacteria, they excrete degradative enzymes into the extracellular environment or tether them to their cell wall
39
What is the nucleoid?
nuclear equivalent in the bacteria; contains all or most of the genetic material but is not surrounded by a nuclear membrane
40
What are 2 things normally seen in EMs of bacterial cells?
ribosomes and cytoplasmic granules
41
What are cytoplasmic granules? When are they usually formed? What function do they serve?
bodies of polymers (ie glycogen, phosphate) formed under conditions of excess nutrients; enables bacterial to store of large quantities of nutrients without increasing the osmolarity of the cytoplasm
42
What is the significance of the cross-linking of polymer chains to form the peptidoglycan layer?
imparts strength and rigidity to the cell wall
43
What is a naturally occuring anti-bacterial agent?
lysozyme (which is found in tears, bodily fluids) splits the glycosidic bonds between NAG and muramic acidd
44
What are two major components of the cell wall?
peptidoglycan + different carbohydrate polymers (ie ribitol, teichoic acid (phosphate), or other sugars)
45
What is ribitol?
sugar alcohol polymer that forms the outer layer of the bacterial cell wall. usually found in Gram +
46
What is teichoic acid? What bacteria is it usually found in?
phosphate polymer that forms the outer layer of the bacterial cell wall; usually found in certain species (ie Staphylococcus (gram +))
47
What is the antibody response of the host usually directed against?
carbohydrate polymers (ribitol or teichoic acid)
48
What is the difference between gram + and gram + bacteria?
Gram + bacteria has a thick layer of peptidoglycan with a layer of different carbohydrate polymers and NO outer membrane. Gram - bacteria has a thin layer of peptidoglycan & outer membrane that contains LPS and an intervening periplasmic space
49
Which bacterium has a periplasmic space? Gram + or gram -?
Gram -
50
What are the components of a gram + bacteria?
Gram + bacteria has a thick layer of peptidoglycan intertwined with a layer of different carbohydrate polymers (ie teichoic acid) and NO outer membrane.
51
What are the components of a gram - bacteria?
Gram - bacteria has a thin layer of peptidoglycan & outer membrane that contains LPS and an intervening periplasmic space (forming a 3 layered envelope)
52
What are porins? What type of bacteria are they usually found in? Why is this medically important?
transport protein found in the outer layer of gram - bacteria; allows entry of nutrients and small hydrophilic molecules by passive diffusion. It is of medical importance because antibiotics can gain entrance into the periplasmic space through porins
53
What roles do the outer membrane of the gram - bacteria serve? (3)
1) blocks entry of large molecules into periplasmic space since it does not contain the transport system of inner cytoplasmic membrane 2) reacts with antibodies 3) barrier to antimicrobial agents/detergents
54
What generally makes gram - bacteria more resistant to antibiotics, antimicrobial agents, and detergents than gram + bacteria? Why?
outer membrane; it doesn't contain transport systems that can allow these things to enter the cell
55
What is vancomycin? What type of bacteria is it most effective against and why?
antibiotic that targets the cell wall. Effective against gram + but NOT gram - because it can't cross the outer membrane (it's too large to fit through the porins)
56
What is LPS composed of? Which component confers antigenic specificity and which confers the toxicity?
polysaccharide (antigen specificity) and lipid A (toxicity)
57
Where is lipid A found?
it is embedded within the lipid bilayer of the outer membrane
58
What is the basis of immunological specificity of the polysaccharide in LPS?
The polysaccharide is composed of an outer layer of repeating oligosaccharide units called "O" antigens . The O antigens (sugars) impart immunological specificity to the cell since they predominate at the cell surface.
59
What are O antigens?
Oligosaccharide units that form the outer layer of LPS; impart immunological specificity to the cell since they predominate at the cell surface.
60
Where is the periplasmic space located? What type of bacteria would you find this in?
Gram - bacteria. Located between the cytoplasmic membrane + outer membrane
61
T/F Gram + are characteristically more resistant to penicillin and detergents
False. It's gram - bacteria that are generally more resistant to these because of the presence of the outer membrane, since it doesn't contain transport systems that can allow these things to enter the cell
62
What is endotoxin? What is an example of endotoxin? What is it responsible for? What type of bacteria is it normally found in?
It is a toxin that is kept "within" the bacterial cell and to be released only after destruction of the bacterial cell wall. Example: LPS - responsible for shock and fever during infections. It is normally found in Gram - bacteria
63
In the gram stain, what step is the differential step to differentiate between gram + and gram - bacteria?
Ethanol treatment step. Only gram - bacteria will decolorize while gram + retain the dye-iodine complex and remain blue
64
In the gram stain, what will happen if you leave the specimens in the ethanol step for too long?
both gram + and gram - cells will decolorize
65
Why is it that gram + bacteria will remain blue while gram - bacteria will decolorize in the gram stain?
gram + have cell walls (thick mucopeptide layer + outer lipid membrane) that are largely impermeable to low m.w. compounds when the organisms are in 70% alcohol, which traps the dye-iodine complex in the cytoplasm. In gram - bacteria, the dye-iodine complex leaks out through the walls (since they contain only a thin layer of mucopeptide layer + outer lipid membrane)
66
What are some of the reasons why a loss in "gram positiveness" occur?
1) if the culture is old (>30 hours) or 2) loss of cell wall integrity through autolytic activity (destruction of a cell through the action of its own enzymes)
67
What is the capsule?
a layer that lies outside the cell wall of bacteria; usually polysaccharide in composition and confers pathogenicity (mutant bacteria that have lost the ability to produce capsule are able to grow in culture but have lost all pathogenicity)
68
How does the capsule confer pathogenicity?
The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (ie prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages
69
T/F flagella are present on every bacteria
False. It is only present on motile bacteria, and not all bacteria are motile. In fact, motile bacteria may become non-motile in later stages of growth or in energy-poor conditions
70
What's the difference between peritrichous flagella and polar flagella?
Peritrichous flagella is when there are many flagella present over the whole surface of a cell. Polar flagella originates from one end of the cell only
71
T/F flagella are easily identifiable through the resolving power of a light microscope
False. It can only be seen in an EM or with a special stain that deposits molecules to increase the diameter
72
How are pili (fimbriae) different than flagella?
they're filamentous surface appendages that are shorter than flagella
73
T/F all bacteria of medical importance of pili
False. Most, but not all, bacteria of medical importance have pili
74
What is the function of pili (fimbriae)?
provides a means of adherence to other cells, either bacterial or animal. Examples: Gonococci produce pili (fimbriae) that bind to specific receptors of cervical epithelial cells, and is an important virulence factor for gonorrhoea
75
What is the F pili?
found on "male" donor strains of bacteria and is necessary for bacterial conjugation (allows for the transfer of DNA from one cell to another).
76
What is the type IV pili?
responsible for the pili-mediated movement, where it extends and retracts and allows for the pushing and pulling of the bacteria across a surface
77
What is the twitching motility? What is responsible for it?
Type IV pili. Responsible for the pili-mediated movement, where it extends and retracts and allows for the pushing and pulling of the bacteria across a surface
78
What are some surface components that allow bacteria to adhere to specific target tissues?
1) specific receptors on host cell surface, 2) glycocalyx or slime layer on host cell surfaces 3) adhesins on the outer membrane of gram - or cell wall of gram + bacteria
79
What bacteriums can form spores?
bacillus and clostridia
80
When do spores form? Is this process reversible?
it's a response to nutrient deprivation. Usually occurs after the log phase of growth. Under favourable conditions the spore can germinate (become an actively dividing bacterium)
81
What are endospores?
a dormant, tough, and non-reproductive structure produced by certain bacteria; formation is usually triggered by a lack of nutrients, and usually occurs in gram + bacteria.
82
What do spores look like when treated with a gram stain?
it will remain colorless because it is resistant to staining
83
What does a vegetative cell mean?
used to describe the reproductive, or non-spore form of a bacteria
84
What are some properties of a spore?
1) they're dormant. 2) resistant to drying, chemicals, and heat (can survive boiling, but not 121˚C)
85
What happens to the properties of a spore when it germinates?
germination is accompanied by a loss of heat resistance, swelling, and uptake of water.
86
T/F all clostridia and bacillus form spores
True.
87
T/F clostridia spores are stable for years
True. Clostridia tetanus spores can survive for long periods in soil and germinate when deposited in deep wounds, causing tetanus
88
T/F Spores are rarely seen in old cultures.
Depends on the bacterial strain - clostridia TETANUS readily forms spores in older cultures but clostridia GANGRENE rarely forms spores. But a general rule of thumb is that spores are rarely seen in very young cultures.
89
What is bacillus anthracis?
bioterror agent
90
T/F Bacillus anthracis are stable for years
True.
91
What triggers bacillus anthracis to germinate?
warm, wet nutrient-rich environment (ie lungs, which results in inhalation anthrax)
92
What agents in growth medium serve as attractants? (positive chemoattractant)
sugars and amino acids
93
What agents in growth medium serve as repellents (negative chemoattractant)
phenols and acids
94
What are "tasters" in the microbiology world?
sensory chemoreceptors on the membrane that control the direction of flagellar rotation
95
What type of movement does CCW rotation of the flagella generate?
straight line movement
96
What type of movement does CW rotation of the flagella generate?
tumbling in place
97
When bacteria are in the presence of an attractant, how do their flagellas move?
the CCW rotation of the flagella dominates, resulting in a straight-line movement towards the attractant
98
When bacteria are in the presence of an repellent, how do their flagellas move?
CW rotation of the flagella occurs until the net movement is properly redirected away from the repellent

Microbiology Quiz 1 (6 decks)

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