TEST #2-CHAPTERS 5,6,7 Flashcards
(100 cards)
1
Q
Define sterilization
A
The complete destruction or removal of ALL forms of microbial life, including the highly resistant and dormant endospores.
- can be achieved by physical (heat, radiation, filtration) or chemical methods
- absolute value
2
Q
Define disinfection
A
The destruction of vegetative pathogens on non-living objects and surfaces.
3
Q
Define commercial sterilization
A
sufficient heating of canned food enough to kill the heat sensitive endospores of Clostridium Botulinum. Any endospores of thermophilic bacteria that my survive won’t germinate under normal storage conditions.
4
Q
Define antisepsis
A
The destruction of vegetative pathogens on living tissue (skin, mucous membranes)
5
Q
Define mucous membranes
A
Membranes that line body openings, including the intestinal tract, open to the exterior; also called mucosa.
6
Q
Define degerming
A
Physically removing microorganisms from a limited area of the skin, a mechanical removal with soap and water; a alcohol pad.
7
Q
Define sanitization
A
Treatment intended to lower microbial counts on eating and drinking utensils (restaurant, café, cafeteria, diner) to safe public health levels.
- Usually accomplished by high-temperature washing or washing in a sink followed by a dip in a chemical disinfectant.
8
Q
Define biocide (germicide)
A
- General methods that kill microorganisms
or - Treatments that cause the death of microbes
9
Q
Define fungicide
A
Kills fungi
10
Q
Define sporocide
A
- Kills endospores
or - Kills highly resistant endospores
11
Q
Define virucide
A
Destroys, inactivates viruses
12
Q
Define bacteriocide (bactericidal)
A
- Kills bacteria
or - Treatments that kill bacteria
13
Q
Define bacteriostatic
A
Treatments that only inhibit (prevents) growth and multiplication of bacteria, once the agent is removed growth resumes.
14
Q
What is sepsis?
A
- Decay or purification
- Bacterial contamination
- Presence of bacteria in normally sterile tissues of the body
- Presence of bacteria in blood actively multiplying
15
Q
What are the factors that influence the rate of Microbial growth?
A
- The number of microorganisms, the more microorganisms there are the longer it takes to remove them.
- Environmental Influences- the presence of organic material (food; bodily fluids) can weaken, neutralizes many of the physical and chemical methods used to control microbial growth.
- Time of exposure- enough time needed to work
121 C (245 F)= 15 psi= 15 min
- if using chemical methods to control microbial growth time of exposure depends on temperature. - Microbial Characteristics affect the choice of physical and chemical control methods.
Most Resistant:
*** Endospores- highly resistant resting structures that some bacteria (Gram positive bacilli) make in response to harsh environmental conditions.
** Mycobacteria- actively growing cells, have a thick waxy wall.
* Gram Negative bacteria- have thin cell walls, have an outer lipid membrane, are external to cell wall, acts as a water-proof barrier.
Least Resistant:
Gram positive bacteria- have thick cell walls, DO NOT have an external lipid membrane to their cells walls, or thick waxy cell walls.
16
Q
What are the actions of microbial control agents on bacterial (prokaryotes)?
A
- Alteration of membrane permeability
* damage to cell membrane and loss of selective permeability results from damage to cell walls. - Damage to proteins denature as inactive proteins.
- Damage to nucleic acids.
17
Q
Define denaturation
A
The loss of a protein’s specific (functional) 3-dimensional shape due to the breaking of the weak hydrogen bonds that kept it in its functional shape.
–hydrogen bonds and denaturation occurs by physical means.–
18
Q
What are the physical methods of microbial control?
A
- Heat
– 2 types of Moist heat sterilization:
A. boiling
B. Autoclave - Pasteurization
- Dry heat sterilization
- Filtration
- Low temperatures
- Desiccation
- Osmotic pressure
- Radiation
19
Q
Heat
A
Kills microorganisms by denaturing their enzymes, resistance varies among different microbes; used for sterilization and preserving canned goods.
- moist heat sterilization kills microorganisms primarily by coagulating proteins (denaturation) 1. Boiling- kills vegetative forms of bacterial pathogens 2. Autoclave- uses steam under pressure; the higher the pressure, the higher the temperature; used to sterilize
20
Q
Pasteurization
A
A mild brief heating of a liquid such as milk, wine, beer, cider, sufficient to kill the organisms that cause spoilage, or disease, without seriously damaging the taste of the product. Lowers microbial numbers
21
Q
Dry heat sterilization
A
Kills by oxidizing effects, flaming, incineration, hot-air sterilization
22
Q
Filtration
A
The passage of a liquid or gas through a screen-like material with pores small enough to retain microorganisms. Used to sterilize heat- sensitive materials, such as culture media, enzymes, vaccines, and antibiotic solutions.
23
Q
Low temperatures
A
The effect of temperatures on microorganisms depends on the particular microbe and t intensity of the application. Ordinary refrigeration has a bacteriostatic effect. Psychotrophs do grow slowly at refrigerator temperatures.
24
Q
Desiccation
A
In the absence of water, microorganisms cannot grow or reproduce but can remain viable for years. Lyophilization or freeze- drying is a process for preserving microbes.
25
Osmotic pressure
The use of high concentrations of salts and sugars to preserve food.
26
Radiations
Has various effects on cells, depending on its wavelength, intensity and duration. Kills microorganisms. There are 2 types:
1. Ionizing
2. Nonionizing
27
Ionizing radiation
1. Gamma rays, X-rays
2. Short wavelengths, less than 1 nm
3. Carries much more energy
4. Very penetrating
5. Causes ionization of water, which forms highly reactive hydroxyl free radicals.
6. Radicals react with organic cellular components, especially DNA
28
Nonionizing radiation
1. longer wavelengths, greater than 1nm
2. Ultraviolet light
3. UV light damages the DNA of exposed cells
4. This damage inhibits the correct replication of the DNA during reproduction of the cell
5. The UV wavelengths most effective for killing microorganisms are about 260 nm
6. These wavelengths are specifically absorbed by cellular DNA
7. A major disadvantage of UV light is that the radiation is not very penetrating (longer wavelengths have less energy)
29
What are the chemical methods of microbial control?
1. Principles of effective disinfection
2. Types of disinfectants
- phenol
- phenolics
- bisphenols
- halogens
- alcohols
- heavy metals and their compounds
- surface-active agents
- quaternary ammonium compounds
- aldehydes
- chemical sterilization
- peroxygens
30
What are the principles of effective disinfection?
- concentration of a disinfectant affects its action
- the nature of the material being disinfected (the presence of organic material)
- the pH of the medium often has a great effect on a disinfectant's activity
- whether the disinfectant will make easy contact with the microbes
- amount of time, and the surrounding temperature
31
Phenol
- 1st widely used disinfectant for surgery
- 1st used by Joseph Lister in 1865; his source was carbolic acid
- mechanism of action is the disruption of plasma membrane, denaturation of enzymes
- used now as a standard of comparison for other disinfectants (phenol coefficient)
- rarely used now because of its irritating qualities and disagreeable odor
32
Phenolics
- Derivatives of phenol that have been chemically altered to reduce its irritating qualities
- Exerts antimicrobial activity by injuring lipid-containing plasma membranes (especially the mycobacterium) and denatures proteins
- Reactive even in the presence of organic material
- Lysol and cresol (surface disinfectants) are examples
33
Bisphenols
- Derivatives of phenol that contains 2 phenolic groups connected by a bridge (bis)
- Hexachlorophene (pHisoHex) is used for surgical and hospital microbial control procedures
- G+ Staph and Strep are susceptible to hexachlorophene
- Excessive use of this bisphenol in bathing infants can lead to neurological damage
- Triclosan, another widely used bisphenol in antibacterial soaps, toothpaste, cutting boards, knife handles
- Widespread use has lead to resistant bacteria
- Action is the disruption of the cell membrane
- Pseudomonas aeruginosa, a G- bacteria, is very resistant to triclosan
34
Halogens
- iodine and chlorine are effective antimicrobial agents
- iodine is 1 of the oldest and most effective antiseptics
- iodine is active against all kinds of bacteria, many endospores, some fungi, and some viruses.
- iodine, a strong oxidizing agent, impairs protein synthesis, alters cell membranes.
- tincture- an aqueous solution of iodine in alcohol
- iodophore- a combination of iodine and an organic molecule which releases iodine slowly. Does not stain and is less irritating.
- chlorine is another widely used disinfectant; its germicidal action is caused by hypochlorous acid that forms when chlorine is added to water.
- hypochlorous acid is a strong oxidizing agent prevents cellular enzymes from functioning
- calcium hypochlorite (chloride of lime used by Semmelweiss in 1840's)
- sodium hypochlorite (bleach)
35
Alcohols
- kills bacteria and fungi but not endospores
- the mechanism of action is usually protein denaturation, but it can also disrupt membranes and dissolve lipids.
- alcohols evaporate quickly and leave no residue
- most of the microbial control activity come from wiping away dirt and microorganisms, along with skin oils.
- alcohols are unsatisfactory antiseptics when applied to wounds they can cause coagulation of proteins under which bacteria continue to grow
36
Heavy metals and their compounds
- several heavy metals can be biocidal or antiseptic, including silver, mercury, copper
- oligodynamic action
- this effect is produced by the action of heavy metal ions on microbes
37
Define oligodynamic action
The ability of very small amounts of heavy metals, especially silver and copper to exert antimicrobial activity
38
Surface active agents (Surfactants)
- Decrease surface tension among molecules of liquid
- Agents include soaps and detergents
- Soap has little value as an antiseptic, but it does have an important function in the mechanical removal of microbes through scrubbing (degermers)
- Soap breaks the oily film on skin into tiny droplets (emulsification) lifting up the emulsified oil and debris
39
Quaternary ammonium compounds
- strongly bactericidal against G+ bacteria, but much less active against G- bacteria
- Fungicidal, amoebicidal, virucidal, but does not kill endospores or mycobacteria
- affects the plasma membrane
- colorless, odorless, tasteless, stable, easily diluted, nontoxic
- organic matter interferes with their activity
40
Aldehydes
- effective antimicrobials
- Ex. formaldehyde, glutaraldehyde, formalin (37% aqueous solution of fomaldehyde gas)
- inactivates proteins by forming covalent cross-links with several organic functional groups on proteins
- formalin was once used to preserve biological specimens and inactivates bacteria and viruses in vaccines
- glutaraldehyde is one of the few liquid chemical disinfectants that can be considered a sterilizing agent
41
Chemical sterilization
- uses a gaseous chemosterilant in a closed chamber
- uses ethylene oxide gas
- inhibits vital cellular functions
- ethylene oxide kills all microbes and endospores.
- it is highly penetrating and doesn't use heat
42
Peroxygens
- group of oxidizing agents that include hydrogen peroxide, ozone, peracetic acid.
- hydrogen peroxide I an antiseptic found in many household medicine cabinets
- it is not a good antiseptic for open wounds, it is quickly broken down into water and gaseous oxygen by the enzyme catalase
- peracetic acid is 1 of the most effective liquid chemical sporocides available and can be used as a sterilant
- ozone is highly reactive form of oxygen
- ozone is often used to supplement chlorine in the disinfection of water because it helps neutralize tastes and odors.
43
What does this describe:
- refers to the number of cells, not the size of cells.
- microbes are "growing" and increasing in number
- microbial populations can become incredibly large in a very short time.
Microbial growth
44
By understanding the conditions necessary for microbial growth, we can:
1. Discourage the growth of microbes that cause disease and food spoilage.
2. Learn how to encourage the growth of helpful microbes and those we wish to study.
45
What are the physical requirements for microbial growth?
1. Temperature (mesophiles, psychrophiles, psychrotrophs, thermophiles)
2. pH
3. Osmotic pressure
46
Mesophiles
- optimum growth temperature of 35-40 C
- The most common type of microbe
- includes most of the common spoilage and disease microorganisms
- the optimum temperature for many pathogenic bacteria is 37 C (98.6 F)
- organisms (normal microbiota) that have adapted to live in the bodies of animals usually have an optimum temperature closer to that of their hosts.
47
Psychrophiles
- "cold-loving" microorganisms
- they can grow at 0 C but have an optimum growth temperature of 15 C
- are found mostly in the ocean's depths and polar regions
48
Psychrotrophs
- can grow at 0 C, but have optimum temperature of 20-30 C, cannot grow above 40 C
- these microorganisms are more common than the psychrophiles an are most likely to cause low-temperature (refrigerator) food spoilage
49
Thermophiles
- "heat- loving" microorganisms
- many of these microorganisms have an optimum growth temperature of 50-60 C (about the temperature of water from a hot water tap, sunlit soil, hot springs)
- many thermophiles cannot grow at temperatures below 45 C; endospores formed by thermophilic bacteria are heat resistant and may survive the usual heat treatment given canned goods (commercial sterilization)
50
pH
- most bacteria grow best between pH 6.5-7.5 (neutral)
- very few bacteria grow at an acidic pH, below pH 4
- some bacteria, called acidophiles, are tolerant of acidity
51
Chemicals in solution (proteins, peptones, phosphate salts) that prevent sudden, drastic changes in pH and which can maintain a specific pH. This is known as:
Buffers
52
Osmotic Pressure
- The concentration of water (solvent) outside compared to inside the cell
- microorganisms obtain all their nutrients in solution from water
- they require water for growth and are made up of 80-90% water
- high osmotic pressure (hypertonicity) removes necessary water from the cell [hypertonic- less water outside the cell than inside; in hypertonic solution, water leaves the cell & plasmolysis occurs]
- this loss of water causes plasmolysis, or shrinkage of the cell's cytoplasm
53
The shrinkage of a cell's contents (including the cell membrane) in a hypertonic solution. But not the entire cell because of its rigid, external cell wall. This is known as:
Plasmolysis
54
What are the chemical requirements for microbial growth?
1. Carbon
2. Nitrogen
3. Sulfur and Phosporous
4. Trace Elements
5. Oxygen
6. Organic growth factors
55
Carbon
- half the dry weight of a cell
| - is the structural backbone of all living matter
56
Nitrogen
- necessary for protein synthesis; is found in all amino acids (the sub-unit building blocks of proteins)
- necessary for the synthesis of ATP, DNA, RNA (nucleotides)
57
Trace elements
- microbes require very small amounts of inorganic metallic ions such as iron, copper, molybdenum and zinc.
- they act as cofactors.
58
Oxygen
- not always a necessity for life, it can often be a poisonous gas
- microbes that use molecular form can produce more energy from nutrients than microbes that do not use oxygen
- obiligate aerobes
- facultative anaerobes
- obligate anaerobes
- aerotolerant anaerobes
- microaerophiles
- organic growth factors
59
- Growth occurs only where high concentration of oxygen have diffused into the medium.
- because oxygen is poorly soluble in a water environment many aerobic bacteria have developed (or retained) the ability to continue growing in the absence of water.
This is known as:
Obligate aerobes
60
- Both aerobic and anaerobic growth
- Greater growth in the presence of oxygen
- Growth is where most oxygen is present, but occurs throughout the tube, although not evenly
Example: E. Coli
- Many microbes are ale to substitute other electron acceptors, such as nitrate ions, for oxygen
Facultative anaerobes
61
- Growth occurs only where there is no oxygen.
- Growth ceases in the presence of oxygen
Example: The genus Clostridium
- These microorganisms can be harmed by toxic forms of oxygen
- toxic forms of oxygen include: singlet oxygen, superoxide free radicals, hydroxyl radical, ozone, and the peroxide anion.
- Because the hydrogen peroxide produced during normal aerobic respiration is toxic, microbes have developed enzymes to neutralize it.
- Catalase converts hydrogen peroxide into water and oxygen gas
2H2O2 ----------------------> 2H2O + O2
This describes:
Obligate anaerobes
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- Are known as "small air lovers"
- Only aerobic growth; oxygen is required in low concentration
- Growth occurs only where a low concentration of oxygen has diffused into the medium
- This limited tolerance is probably due to their sensitivity to superoxide free radicals and peroxides, which they produce in lethal concentrations under oxygen-rich conditions
This describes:
Microaerophiles
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- Essential organic compounds an organism is unable to synthesize
- Micronutrients; they must be directly obtained from the environment
- 1 group are vitamins that act as coenzymes
This describes:
Organic growth
64
What is the criteria a useful culture medium must meet?
1. It must contain the right nutrients for the specific microorganism (chemical requirement)
2. It should contain sufficient moisture, a properly adjusted pH (physical requirement)
3. A suitable level of oxygen (or none at all)
4. The medium must initially be sterile before inoculation; it must be able to be sterilized.
5. It must be able to be incubated at a proper temperature for growth.(usually 37 C= 98.6 F)
65
What are the types of culture media?
1. Based on their ingredients:
- Chemically defined media
- Complex media
2. Based on what they do:
- reducing media
- selective media
- differential media
- enrichment culture
66
What is chemically defined media?
- A microbiological growth medium whose exact chemical composition is known
- Provides an energy source as well as sources of carbon, nitrogen, sulfur, phosphorous, and any organic growth factors the organism is unable to synthesize
- organisms that require many growth factors are described as "fastidious"
67
This describes what kind of media?
- A microbiological growth medium made up of nutrients including extracts from yeasts, meat or plants or digest of proteins from these and other sources.
- The exact chemical composition varies slightly from batch to batch
- In complex media, the energy, carbon, nitrogen, and sulfur, requirements of the growing microorganisms are provided by protein.
Complex media
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This describes what type of media?
- A microbiological growth medium that contains ingredients that chemically combines with dissolved oxygen and removed oxygen from the medium.
- Used to grow and maintain anaerobic bacteria
Reducing media
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This describes what type of media?
- A microbiological growth medium designed to suppress the growth of unwanted bacteria and encourage the growth of the desired microbes.
- In clinical and public health microbiology, it is frequently necessary to detect the presence of specific microorganisms associated with disease or poor sanitation.
Selective media
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This describes what type of media?
- Used in the differentiation of colonies of desired microbes from others
- A microbiological growth medium that can distinguish a specific microorganism species from others based on a color change due to some unique metabolic step or process of that 1 species
- Makes it easier to distinguish colonies of the desired organism from other colonies growing on the same plate
Sometimes selective and differential characteristics are combine in a single medium
Differential media
71
What does this describe?
- A microbiological growth medium designed to grow to large detectable numbers microorganisms from an initially small inoculum.
- Bacteria present in small numbers can be missed
- An enrichment culture is usually liquid and provides nutrients and environmental conditions that favor the growth of a specific microbe but not others.
- selective medium designed to increase very small numbers of the desired microorganism to detectable levels.
Enrichment culture
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A process in which a pure culture of microbes is placed in a suspending liquid and quick frozen at temperature ranging from -50 to -95 C.
This is known as:
Deep- freezing
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- A suspension of microbes is quickly frozen at temperature ranging from -54 to - 72C
- The ice is then removed by a high vacuum (sublimation)
- The remaining powder-like residue that contains the surviving microbes can be stored for years.
This is known as:
Lyophilization (freeze- drying)
74
What are the phases of growth?
1. Lag phase
2. Log phase
3. Stationary phase
4. Death phase
75
The initial phase in the bacterial growth curve. No cells are dying, but no new cells are forming. Not dormant; 1st the inoculum is adjusting to the new medium and a intense metabolically active time of preparation ("gearing up") for cell division.
This phase is known as:
Lag phase
76
A period in which ALL the microorganisms are rapidly dividing, shortest generation time. metabolically active (vegetative cells). * All are sensitive here to anything that could affect their growth.
This phase is known as:
Log phase
77
The bacterial cells levels off, the number of new cells forming equals the number of cells dying. Because:
a) the nutrients in the media are begging to be used up
b) the accumulation of metabolic wastes are beginning to pollute, poison the media.
This phase is known as:
Stationary phase
78
All the nutrients in the media are used up, and the accumulation of toxic metabolic wastes have poisoned the cells. (use or make endospores).
This phase is known as:
Death phase
79
What does this describe?
- Viable cell count
- Standard plate count
1. Serial dilution
2. Pour plate method
- Positive: very accurate. only living cells form visible colonies
- Negative:
1. many steps, each 1 a possible route for contamination
2. uses a lot of sterile lab equipment (sterile water blanks, sterile pipettes, media, sterile petri-dish)
3. not immediate results, you need at least 24 hrs incubation
Direct measurements of microbial growth
80
What does this describe?
- uses turbidity (cloudiness in a nutrient broth & optical density); light absorbency
- light transmittance- the amount of light that goes through the sample & isn't absorbed
- optical density (light absorbed)- the amount of light that is absorbed in the sample
- Negative: not as accurate because dormant cells, dead cells, cells fragments, dirt, finger prints ALL absorb light.
- Positive:
1. 1 step procedure
2. only 1 piece of equipment, spectrophotometer (100 changes for contamination)
3. Immediate results
Indirect measurement of microbial growth
81
The non-protein component of an enzyme; a non-protein organic molecule (such as vitamins) that attaches to an enzyme to make it functional.
This is known as:
Coenzyme
82
The complete, whole, active enzyme. Together the apoenzyme and cofactor (or coenzyme) forms this:
Holoenzyme
83
What factors influence enzymatic activity?
1. Temperature- molecules move more slowly at lower temperature and may not have enough energy to cause a chemical reaction (bacteriostatic); high temperatures denatures enzymes (bactericidal)
2. pH- most enzymes have optimal pH, above or below this pH value, enzyme activity (and reaction rate) declines (bactericidal)
3. Substrate concentration- there is maximum rate at which a certain amount of enzyme can catalyze a specific reaction, under conditions of high substrate concentration, the enzyme is said to be in saturation
84
The active site on the enzyme is always occupied by substrate or product molecules.
This is called:
Saturation
85
The removal of electrons from an atom or molecule (a reaction that often produces energy).
* most biological oxidations involve the loss of hydrogen atoms (dehydrogenation)
This is called:
Oxidation
86
The gain of one or more electrons
This is called:
Reduction
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Organisms that use light as their primary energy source; obtain energy from sunlight.
This is called:
Phototrophs
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Organisms that depend on oxidation- reduction reactions of inorganic or organic compounds for energy; obtain energy from chemical compounds.
This is called:
Chemotrophs
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"self-feeder"- organisms that use inorganic carbon dioxide gas as their carbon source; obtain their carbon from inorganic carbon dioxide gas.
This is known as:
Autotrophs
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"feeders on others"- organisms that require pre-formed organic molecules as their carbon source; obtain their carbon from pre-formed organic compound.
This is called:
Heterotrophs
91
What does this describe?
- Obtain energy from sunlight; carbon from inorganic carbon dioxide gas
- Organisms that use light as a source of energy and carbon dioxide as their chief source of carbon
- Includes photosynthetic bacteria, cyanobacteria, algae, and green plants.
Photoautotrophs
92
What does this describe?
- Use the same organic compound as energy; carbon source.
- Organisms that use the same organic compound (ex: glucose) as their energy and carbon source
- saprophytes- obtain nutrients from dead organic material
- parasites- obtain nutrients from living host
Chemoheterotrophs
93
What does this describe:
- A few unusual bacteria that use light as a source of energy and organic compounds (alcohols, fatty acids, organic acids, carbohydrates) as sources of carbon
Photoheterotrophs
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What does this describe:
- A few unusual bacteria that use the electrons from reduced inorganic compounds (hydrogen sulfide, sulfur, ammonia, nitrite ions, hydrogen gas, iron, carbon monoxide) as a source of energy, and inorganic carbon dioxide gas as a carbon source
- lithotrophs; "rock eaters"
Chemoautotrophs
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The final electron acceptor is oxygen and water is the final end product.
This is called:
Aerobic respiration
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The final electron acceptor is an inorganic substance other than oxygen, water is not a final end product.
This is called:
Anaerobic respiration
97
A metabolic process that releases energy from a sugar (or other organic molecule), does not require oxygen, and uses an organic molecule as the final electron acceptor.
- produces only small amounts of ATP (1-2 ATP molecules)
This is called:
Fermentation
98
The addition of a phosphate group to a chemical compound.
- organisms use several mechanisms to generate ATP from ADP
This is called:
Phosphorylation
99
What is the generation of ATP?
1. Substrate- level phosphorylation- ATP is generated when a high-energy phosphate group is directly transferred from a phosphorylated compound (substrate) to ADP
2. Oxidative phosphorylation-
a) electrons are transferred from organic compounds (ex: the oxidation of glucose)
b) then the electrons are passed through a series of different electron carriers
c) the final electron acceptor could be oxygen (aerobic respiration) or other inorganic molecules (anaerobic respiration) organic molecules (fermentation)
d) this process occurs in the plasma membrane of prokaryotes
100
- the 1st stage in carbohydrate catabolism
- it occurs in most living cells
- 1 molecule of glucose is split into 2 molecules of pyruvic acid.
This describes:
Glycolysis
