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74 Cards in this Set
- Front
- Back
psychorphiles
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grow at temperatures below 0 to 15C
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Mesophiles
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grow between ~15-45C
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Thermophiles
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grow between 40-80C
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Hyperthermophiles
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grow above 100C
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Minimum growth temp
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the cells are growing but it is so slow that it is incompatible with survival
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Maximum growth temp
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a steady decline from the optimum growth temperature
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Optimal growth temperature
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cells are most comfortable, as evident with their growth rate.
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when an organism gets towards maximum growth temp, what can happen to the cells macromolecules
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denaturation can occur
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Which of the species used in this exercise would you expect to be most likely to cause spoilage of refrigerated food?
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Arthrobacter
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what species from Lab 10 would be able to grow most rapidly in the human body?
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Micrococcus and E.coli because it has the highest growth avg. for 37C
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what is osmosis
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the process in which water flows from one side to the other of a semi-permeable membrane.
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what is the force that drives osmosis?
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the movement of water molecules is driven by osmotic pressure.
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what directs the diffusion of water during osmosis
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water will flow depending ont he difference in the concentration of water molecules between both sides of the membrane. (will flow to a side with lower water concentration)
also it is attracted to places with a lower solute concentration. |
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what are the three enviornments a microbe can experience with regards to osmotic pressure
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Isotonic
Hypertonic Hypotonic |
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what is an isotonic environment
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there is no net flow of water across the membrane because there is an equal concentration of solutes inside and outside.
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what is a hypertonic environment?
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environment were there is much higher concentration of solutes outside the cell than inside.
water will flow out draining the cell of water. |
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what will happen to the cell during a hypertonic environment
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the plasma membrane will shrink which is known as plasmolysis.
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define halotolerant
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can grow at low to moderate salt concentrations
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what are halophiles
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actually require the high salt environment for growth.
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define hypotonic environment
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much lower of concentration of solutes outside the cell than inside.
water will from the outside to the in which will lyse the cell. |
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what is a neutral solution (in terms of pH)
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7.0
has an equal amount of protons and hydroxyl ions |
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what is an acidic solution (pH)
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0-6.99
has an excess of protons or a deficiency of hydroxyl ions |
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what is an alkaline solutions (pH)
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7.01-14
have excess hydroxyl ions or a deficiency of protons |
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relativity of the pH scale and protons
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a change of one number on the pH scale is equivalent to a 10-fold increase/decrease in the number of protons
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how can an acidic solution reduce its pH
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acid can donate its protons to water (if it is added to water) which can reduce its pH
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how can an alkali solution increase its pH?
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if added to water, the hydroxyl can donate its ions to the water, increasing its pH
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environment acidophiles live in
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acidic, low pH environments
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alkaliphiles environment
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live in high pH environments
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environment for neutralophiles
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live at near neutral pH levels.
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define strict aerobes
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micrococcus species, have an absolute requirement for oxygen and depend on aerobic respiration for growth
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strict anaerobes
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the clostridium species
for some of these organisms, exposure to O2 is fatal, they depend on anaerobic respiration and/or fermentation for growth |
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Facultative mcirobes
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are a very adaptable class of microbes where they can grow either int eh presence or absence of oxygen (aerobic respiration or anaerobic/fermentation)
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how do you grow microbes that cannot grow in an aerobic environment?
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use thioglycollate media
it is a reducing agent that effectively removes oxygen from the environment. |
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why is thioglycollate a good media for anaerobic growth?
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it reacts with and sequesters the oxygen in the media.
and oxygen gradient is established - the portion at the interface between the air and the medium is somewhat aerobic while the deeper regions become increasingly anerobic. |
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what is resazarin?
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an indicator for the amount of oxygen in a thioglycollate broth tube - should be colorless in anaerobic conditions, and will turn pink if it is exposed to oxygen.
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what are cidal agents?
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a chemical which prevents growth through permanent destruction of a cell
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static agents?
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a chemical which prevents growth by slowing or stoping growth but if the agent is removed, growth may resume.
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what's a sterilant?
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sterilization is a term used to describe the destruction of al organisms in or on something.
this includes all organisms on a surface or in a fluid. |
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What's a disinfectant
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used to describe processes that lead to the reduction in the number of pathogens to harmless levels.
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if an object is disinfected, is it sterilized?
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no, it is just no longer capable of causing disease.
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are disinfectants ok to use on body?
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no they are too harsh to use on tissues, reserved to cleaning surfaces.
and they do not destroy bacterial endospores |
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what are antseptics give an example
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a chemical that is used on tissue to destroy or inhibit the growth of microorganisms.
an example would be hydrogen peroxide which will effectively clean a cut but it will cause moderate tissue damage. |
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define santization
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the process of removing microorganisms to reduce contamination to safe levels.
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what is a phenol coefficient
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quantitative assessment of the effectiveness of a compound as a disinfectant.
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look over phenol coefficient paragraph from antiseptic lab
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how do soaps and detergents work in preventing growth
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work by dissolving the plasma membrane
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how do halogens prevent growth and give examples of halogens
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denature proteins.
ex. is iodine and chlorine |
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how do alcohols prevent growth and give examples
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dissolving the plasma membrane and can denature proteins.
ex. isopropanol (rubbing alcohol) and ethanol. |
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How do phenolics prevent growth and give examples
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dissolve the plasma membrane and denature proteins.
ex. lysol, pHisoHex hand wash |
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how do oxidizing agents prevent growth and give examples
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oxidation of biological macromolecules
ex. hydrogen peroxide. |
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what's an antibiotic
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a chemical that exhibits the property of selective toxicity (a chemical that is poisonous to a microbe yet harmless to the human or animal host)
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what is the principle of selective toxicity
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it exploits the differences in cellular structure and metabolic pathways that exist between animal host and the infectious agnet
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what is the key difference between antiseptics/disinfectants and antibiotics
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selective toxicity: while all agents are toxic to bacterial and human cells, only antibiotics preferentially target bacteria.
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what are the two effects antibiotics have?
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-static
-cidal effect |
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bacteriostatic drugs
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slow the growth of organisms but do not kill organisms
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bactericidal drugs
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kill the organism and are usually more effective on actively growing cells.
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how is the effectiveness of an antibiotic described
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it can be described in terms of its
spectrum and sensitivity/resistance of the bacterial pathogen to a particular antibiotic. |
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what is the antibiotic spectrum
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describes the range of species that are sensitive to the antibiotic
there are "broad" and "narrow" range antibiotics |
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sensitivity/resistance for describing antibiotic effectivness
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whether or not particular bacterium can be inhibited or killed by the drug
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effective antibiotic treatment requires the bacterium to be sensitive to and also within the range of an antibiotic
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remember that
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ways a cell can affect bacterial growth
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inhibition of cell wall synthesis
inhibit protein synthesis inhibit nucleic acid synthesis competitive inhibition of enzymatic activity |
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what antibiotics inhibit peptidoglycan synthesis
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penicillin
ampicillin cepatholothin vancomycin |
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what antibiotics inhibit bacterial protein syntehsis
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tetracycline
erythromycin |
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if a particular bacterial strain is sensitive to an antibiotic what will happen
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a circular zone/clearing and inhibition is observed surrounding the disk.
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what will ultimately determine the resistance of a bacterial strain to an antibiotic
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depends on the SIZE of the zone of inhibition.
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what region of the electromagnetic spectrum does UV light occupy?
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100-400 nm
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UV light and its effect on cells
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damages cells because DNA absorbs light of this wavelength.
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what can happen to DNA when exposed to UV light
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a mutation known as thymine dimer.
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what are thymine dimers
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formed when UV leads to a covalent linkage between adjacent thymine residues on the same DNA strand.
leads to a distortion in the shape of the double helix and results in errors during replication. |
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T/F UV light penetrates the surface for deep damage
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False, UV light is not very penetration and so its effects are limited to the surface this exposed to the radiatin.
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what are the variables that influence the effectiveness of UV light as a germicide
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1. the type of wavelength (shorter about 260 nm are > that longer)
2. duration of exposure (longer > shorter) 3. type of organism (endospores are more resistant than vegetative) 4. Activation of the cellular DNA repair machinery (if the DNA repair system is overwhelmed, many mutations can accumulate) |
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ultraviolet is between what two numbers on the electromagnetic spectrum
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100 -400 nm
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visible light on the electromagnetic spectrum
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400-750nm
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infrared on the electromagnetic spectrum
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450-1000nm
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