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105 Cards in this Set
- Front
- Back
psychorophile |
less than 15 detgees celcius |
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mesophile |
grows between 20 and 45 degrees celcius |
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S, aureus is a |
mesophile |
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limitations of boiling water for sterilization |
endospores and thermoduric species will not be killed by boiling water |
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what has the widest range of temperature tolerance |
spores and bacillus species |
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least tolerant to higher temperatures |
Pseudomonas aeruginosa |
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thermoduric bacteria |
bacteria that survives boiling but does not grow |
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what are buffers used for in culture media |
to neutralize alkaline or acidic metabolites produced during growth |
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why do microbes differ in their pH requirements |
enzymes required for metabolism and growtj may have different pH optima for different microbes |
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what inhibits microbial growth at nonoptimal pHs |
enzymes will function at rates lower than their potential at optimal pH |
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What is the pH tolerance of bacteria compared to yeasts? |
yeasts grow better at higher hydrogen ion concentrations (lower pH) than bacteria |
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yeasts grow |
at a lower pH than bacteria |
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buffer systems used in microbial media |
peptide buffers, phosphate buffers, and bicarbonate buffers |
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define a buffer |
a combinatin of chemical compounds that rsist pH change since they will neutralize Hydrogen and hydroxide and maintain a constant pH |
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simply define a buffer |
one that maintains a constant pH |
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how do microorganisms change the pH of their own enviorment |
they produce biproducts that change the pH |
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isotonic solutions |
have equal concentrations of solute inside and outside the cells |
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hypotonic soultions |
have a higer concentration of solute inside the cell than outside the cell |
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hypertonic solutions |
soultions have a higher concentration of solute outside of the cell than inside the cell |
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osmosis |
the movement of water acrosse a semipermeable membreane in response to differing soulte concentrations on each side. |
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osmotic pressure |
the force developed within a cell due to movement of water across the cell membrane due to unequal solute concentrations |
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plasmolysis |
when the plasma membrane shrinks away from a cell wall due to a hypertonic solution |
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halophilic |
bacteria that tolerate and grow well in hypertonic salt solutions |
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how is it possible for bacteria to grow in a hypertonic enviorment |
bacteria have membrane structures that can resist plasmolysis and restrict water flow from the cell at high salt cocentrations |
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What concentrations of NaCl are omptimal for most bacteria |
at or below seatwater, between .5-,85% |
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H.salinarium |
can tolerate high salt concentrations (halophilic) |
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foods high in salt |
bacon ham olives canned meat pickles |
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why dont bacteria lyse when placed in a hypotonic solution |
they have a rigid cell wall that restricts membrane expansion and prevents lysis |
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what are limitations of a test such as the one performed on the evaluation of a disinfectant |
evaporation, dilution in the natural enviorment and also inactivation of the disinfectant |
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a good infectant is one that |
easily and quickly diluted and applied, kills all microbes in a short period of time, is inexpensive, and is safe under normal use conditions |
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what is the phenol coefficent technique |
comparison of a disinfectant with a standard phenol solution that kills all the microorganisms under study within 10 minutes but not within 5 minutes |
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disinfectants that are more effective than phenol have a coefficent |
coeffiecent greater than 1
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disinfectants that are less effective than phenol have |
a coefficent less than one |
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how to determine phenol coeffcient |
the concentration of the dilution of disinfectant is divived by the concentration of dilution of phenol |
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microbicidial |
referes to killing of microorganisms |
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microbiostatic |
refers to inhibiotn of growth of microorganims |
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factors that influence the activity of a disinfectant |
temperature, pH and humidity |
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why do microorganisms differ in their response to disinfecrants |
the strucutre of the cell wall may differ resulting in variabl eeffects |
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how can you determine whether the zone of inhibition is due to death or inhibition of bacterium |
you could subculutre from the zone of no grwoth into the fresh media and see if any microbes grow from it |
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what factors must be carefully controlled in the kirby-bauer method |
amount of bacteria inoculated, distribution of inoculum, incubation period, antibiotic diffusion rate, concnetration of antibiotic, and growth rate of bacteria |
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in which phase is bacterium most sensitie to an antibiotic |
early exponential phase cultures are most sensitive |
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if the clinical laboratory reports bacterial susceptibility to an antibiotic but the patient is not responding to it what could be wrong? |
clerical error, contamination, or the wrong culture could have been tested |
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what are the similarites and difference in response to plates with gram-positive bacteria and gram-negative bacteria, |
different zones of inhibition indicate effectiviness for the same antibiotics, the diameter of the zone is different, a different series of antibiotics is tested against each group of microbes |
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what is the difference between an antibiotic and and antimicrobic |
an antibiotic is produced by a microorganism and is effective agains microorganisms and an antimicrobic is a naturally occuring or man made chemical agent effective against microorganisms |
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why are bacteria becoming more resistants to antibiotics |
the more they are used the more probability to become resistant, use of orally antibiotics that make contact with common organisms in the difestive tract can produce resustant strains, use of antibiotics in animal feeds for commerical animals for food |
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Why are coliforms selected as the indicator of water potability? |
They indicate the presence of lactose-fermenting gram negative rods. If they are present, the water may contain fecal microbes. and is not potable |
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Does a positive presumptive test indicate the water is potable? |
not it suggests the water is not potable |
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Why is the MPS test qualitative rather than quantitative
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It estimates the probable number of microorganisms in 100ml of water without actually counting them. |
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function of lactose broth in the MPN test |
presumptive indication of coliforms |
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Function of Levines EMD or LES Endo agar |
used for the completed test indicating the presence of coliforms |
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nutrient agar slant function in MPN |
used for gram staining the culutre to determine the presence of gram negative rods |
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gram stain |
shows whether the organisms present in the presumptive and confirmed tests are really gram negative rods |
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what does a metallic green sheen indicate on an EMB plate? or pink to dark red colonies with a metallic surface sheen on LES Endo agar? |
These results indicate the presence of coliforms in the completed test |
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What bacterial diseases can be transmitted by polluted water? |
diarrhea, atypical penumonia, camplyobacteriosis, UTIs, ear infections, cholera, typhoid fever, bacterial dysentery and hemorragic fever, |
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What does a postive colilert-18 test indicate? |
that fecal colifomrs such as E.coli form human or animal intestinal tracts are present, |
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What does a negative colilert-18 test indicate |
that total coliforms and E.coli are absent and not in the water sample being tested |
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Why were three different media used in the enumeration of soil microbes expirment |
because not all the microbes present will grown on any one medium. |
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The three types of media that were used in soil enumeration experiment |
Sabourauds dextrose agar for fungi glycerol yeast extract for actinomycetes (filamentous oil bacteria) TSA - common typical bacteria |
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Would the same results be obtained if the sample was collected during a different time of the year? |
Yes. vegetable decay may be selective. as well as temp. and soil moisture. and abundance of plants at certain times of the year |
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When general groups of soul bacteria cannot be determinedusing the media and procedures in this exercise? |
obligate anaerobes |
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what generilations can you make from this exercise with respeect to your garden soil? |
whether it is alkaline or acidic, (fungi in acidic) soil fertility based upon amount of microbes present |
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What are some physical features of soil that influence microbial populations |
porosity, that allow moisture to enter soil the ph of the shoil the quantity and availability of nutrients in the soil |
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what is the compostition of glycerol yeast agar? |
glycerol, agar, ferrous sulfate, sodium propionate, asparagine, |
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Why are different dilutions used for bacteria fungi and actinomyecetes? |
thbecause in most soils there will be a greater number of typical bacteria, followed by the actinomycetes, and finally the least, comprising fungal isolates |
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Why is a standard plate count perfomed on food products? |
to determine the number of microbes in 1g of food. if greater than 10^6 per gram it may be hazardous to consume |
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does the number of bacteria recorded by the standard plate count method accurately reflect the total bacterial count from that sample? |
no because many microbes present may not grow in the medium utilized |
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why are 25 - 250 colonies used for calculations? |
this range allows a reasonably accurate count while not requiring excessive time to perform |
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why is a 20g sample of hamburger blended with 180ml of diluent to yeild a 1/10 dilution before making further dilutions? |
the consistincey of the sample would not allow accurate pipetting and subsequent dilutions if not first treated in this manner |
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food poisoning? |
food containing microbes |
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food intoxication |
the microbe may no longer be alive, but toxins it produced are in the food |
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why use plant count agar in food procedure |
grows many of bacteria found in food, is light in color and facilitates colony counting |
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why should hamburger not be repeatedlly frozen and thawed? |
eacg time it is thawed the microbes increase in number and remain viable upon refreezing |
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could a type AB indivdual receive blood from a type B individual? |
yes the type AB pereson does not prudce antibodies against type A or type B |
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Who would receive type O blood? |
all blood types |
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could a person with blood type AB receive blood from a primate with the same blood type? |
no because it is a different species, and does not have histocompatible antigens |
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why cant u give a type A type B blood |
the donor blood cells would agglunitate in the recipeintes ciruculatory system by anti-B antiboides already present leading to blocakge of blood vessels |
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What cause clumping to occur? |
the antigens on the surface of the red blood cellsare bound and cross-linked by specific antibody linking the blood cells together in agllutination complexes |
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What is a hemagglutination reaction? |
the linking of particulate antigens by antibody resulting in visible complexes |
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what is serotyping? |
serotyping uses agllutination or precipitin reactions to diagnose an infection in an individual or, as in this exercise to determine the type of antigens on an individuals red blood cells |
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MPN test |
used to determine water quality, it is a series of test to determine the number of cloiforms in a water sample, consists of a presumptive, confirmed and completed test |
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in the presumptive test |
watch for a bubble in Durham tube means positive for lactose fermentation by coliforms |
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in the confirmed test |
use EMB plate to determine the presenceo f E.Coli from the water smaples |
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completed test |
gram stain for gram negative bacteria |
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Postitive results in the quickvue in-line strep A test? |
two lines, one red one blue, blue is the control line, red line mean positive for strep |
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Absorbacne equals |
2-log(%T) |
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alkalinophiles |
ph between 8.6-11 optimal at 10 |
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halophiles |
salt concetrations at .3-.8 M extreme at 3.4-5.1 M |
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acidophiles |
pH at 2.0 or below |
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psychrophiles |
under 20 degrees C |
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ELISA test does? |
measures antibodies in your blood, used to determine if you have antibodies related to certain infections and is use to diagnose infections and diseases |
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The entreopluri test is used to |
identify enterobacteria and other gram negative oxidase negative bacteria |
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in the plaque assay is used to |
determine the concentrarion of virions |
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why do we dilute the phage suspsension? |
to avoid overgrowth of number of plaques |
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concentration of plaque forming units (PFU/ml) |
number of plaques that form in assay / dilution factor |
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Conjugation |
living bacteria transfers DNA through sex pilus to other living bacteria |
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Transformation |
living bacteria picks up exogenous DNA from surroundings left behind by dead bacteria |
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Competence |
ability of a bacteria to gain foreign DNA by transformation |
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Induction |
using calcium chloride and heat shocking to make a cell competent |
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a plasmid contains |
an origin of replication, multiple cloing site, promotor, and a selectable marker |
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mutiple cloing site is the |
area where the gene of choice is inserted using restriction enzymes |
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selectable marker |
the resistance gene that only allows transformed (cells that has the marker) cells to grow when places on plates with that drug |
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GFP |
green flurorescent protein isolated from jellyfish, shows green for successful transformation |
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IPTG does what? |
removes the repressor and allows GFP to be transcribed and expressed |
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The kind of plates used in the transformation |
ampicillin resistance plates, which is select for transformants |
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purpose of heat shocking the cells |
it facilitates entry of DNA into cells |