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Micro Lab Test 2
Terms in this set (102)
Which of the following are selective media?
HEA, EMB, cCNA,
A colony picked directly from ______ media should never be considered a pure culture
The dyes eosin Y and methylene blue
the antibiotics colistin and naladixic acid
what would be the volume of the of a cube measuring 10,000 micrometers on each side?
From our laboratory manual, regarding urease test 1: Is it acceptable to record positive urease test results early, before the suggested incubation time is completed? Is it acceptable to record a negative result early, before the suggested incubation time is completed?
positive yes, but negative no
Nitrate reduction test - reduction of nitrate to nitrite
Red color after addition of reagents A and B
media is liquid, control is solid
Nitrate reduction test - reduction to nongaseous nitrogenous compounds
no color change after zinc dust
Addition of 300 microliters sample to 2.7 milliliters diluent is a ___ fold dilution
Addition of 30 microliters sample to 2.97 milliliters diluent would be an ____ fold dilution
Mike Robe takes his gelatinase test out of the incubator. He notices that all of the tubes are liquid, including his negative control. What can he conclude?
The heat from the incubator melts the gelatin. He should place his tubes in the fridge until the negative control becomes solid. Then, he can read his results
For the nitrate reduction test, the color red always indicates a positive result.
Which set of Phenol red carbohydrate fermentation test results shown would be most trusted and reliable?
From our laboratory manual, regarding the phenol red carbohydrate broth tests: Suppose you inoculate a PR-glucose broth with an organism known to be a slow-growing fermenter. After 48 hours, you see slight turbidity, but read it as negative for gas, and negative for acid production... Is this result a false positive or a false negative?
From our laboratory manual, regarding the Phenol red carbohydrate broth tests: Suppose you inoculate a PR-glucose broth with an organism known to be a slow-growing fermenter. After 48 hours, you see slight turbidity, but read it as negative for gas, and negative for acid production... Is this false result caused by poor specificity or poor sensitivity of the test system?
From our laboratory manual, regarding triple-sugar iron agar (TSIA): The sulfur reduction test is not able to differentiate H2S produced by anaerobic respiration and H2S produced by putrefaction. Is this inability the result of poor sensitivity or poor specificity of the test system?
Which of the following sugars was NOT included in our TSIA slants?
What is happening to the bacteria at a molecular level when exposed to extreme heat?
The proteins denature causing them to be ineffective
In Ex. 6-6, at T0 we will transfer 1.0mL of E. coli to a heated flack in the water bath. Why don't we just put the whole test tube containing the original sample of bacteria directly into the water bath? (What is the purpose of transferring to the heated flask?)
The broth we transfer the bacteria to is already at the correct temperature. If we put the whole test tube in, it would have to heat up, and that would not be the true T0.
Which species would be mostly likely to withstand high temperatures (>60C) or other extreme conditions?
The bacteria we work with in this class (as well as most human pathogens) would be considered :
At temperatures ABOVE the cardinal temperature of a bacterial species, the rate of cell division _____________; at temperatures BELOW that cardinal temperature, the rate of cell division ____________.
From our laboratory manual, regarding the Vogues-Proskaur test: Would a false negative result for the VP test more likely be attributable to poor sensitivity or to poor specificity of the test system?
A positive reaction for cysteine desulfurase production in SIM medium would produce
a black precipitate in the medium.
The methyl red test is intended to detect organisms that are capable of:
performing mixed acid fermentation of glucose.
If the addition of Kovac's reagent produces a floating red layer on a SIM medium culture, this
indicates the organism is
In the Antimicrobial Suseptibility Test using the Krirby-Bauer Disk Diffusion method, if an organsm that is susceptible to an antimicrobial agent, a clear _____________________ will appear around the disk where the concentration is high enough to stop growth.
Zone of inhibition
What is the MIC as it pertains to the antimicrobial susceptibility test
Minimum inhibitory concentration, which represents the minimum concentration of that animicrobic agent that can be used to inhibit growth of that bacteria. It is marked by the junction between the zone of inhibition and bacterial growth.
A chemical that punctures cell walls would most likely be considered:
A disc containing 10 μg of penicillin was measured to have a volume of 2 μL. Calculate the concentration of penicillin in this disc (in grams per liter)
In the Kirby-Bauer antibiotic disk sensitivity testing procedure (described & used in exercise 7-3), which of the following processes creates a gradient of antibiotic concentration?
passive diffusion (random movement of substances through semi-solid media)
The original concentration in a sample is 2 x 10^6 CFU/mL (colony-forming-units per milliliter). Application of which sample volume would, in theory, yield a plate having 200 colonies
A test that has high sensitivity but poor specificity can result in ________________ . A test that has high specificity but poor sensitivity can result in ________________ .
false positives, false negatives
Which of the following gives the correct oberservations of positive test results for these tests: 1.) sulfur reduction, 2.) mixed-acid fermentation, 3.) citrate ultilization,4.) glucose fermentation.
1.) black, 2.) red, 3.) blue, 4.) yellow.
A bacterial species was shown to ferment lactose (ie it is a coliform). Assuming these results are correct, what else can we reasonably conclude about the bacterial species?
It can also ferment glucose and It is not P. aeruginosa, since it is known that P. aeruginosa is a non-fermenter
On Tuesday's lab, we will be performing the Ames test. We will perform a ____________ plates of bacteria before we add potential mutagen-soaked disks. To inoculate the plates, we use ____________.
spread, a metal "hockey-stick"
Which ingredient in cCNA with 5% sheep blood agar supplies Carbon?
Casein, animal tissue, yeast extract, beef extract, and corn starch
Which ingredients in cCNA with 5% sheep blood agar supplies nitrogen?
protein and nucleic acid. Casein, animal tissue, yeast extract and beef extract. Not corn starch
is cCNA agar a defined or an undefined medium?
would removing colistin and nalidixic acid from CNA alter the mediums sensitivity or specificity?
Why might colistin affect Gram- negative bacteria more severely than Gram -positive bacteria?
cCNA affects the membrane. Gram positive have a thicker peptidoglycan wall
Which temperature would be most suitable for cultivation of bacteria that colonize mammals?
36.5 degrees C
How many microns per centimeter?
Which of the following statements is false?
experimental controls are wasteful and not strictly necessary
From your laboratory manual: "Some microbiologists recommend re-incubating organisms producing methyl red- negative results for an additional 2 to 3 days" ... why?
To increase test sensitivity
If an organism has a mean growth rate of 4 generations per hour, what is its mean generation time?
A colony picked directly from ____ media should be considered a pure culture.
What type of material is agar?
Which pH indicator is used in Simmon's citrate media?
Which of the following would be most likely to cause false positives on a diagnostic test?
low test specificity
approximately how many Staphylococcus epidermis bacteria could fit into a cube that measures 1 millimeter on each side?
Which of the following can be fermented?
suppose a student testing an unknown culture performs the urease test according to the protocol; after the specified incubation, the media has not changed color... Which of the following conclusions would be most proper/ justified?
No urease activity was observed
The properties and function of the enzyme tested in the gelatinase test suggest that it is most likely?
Fluid thioglycollate medium an indicator, _____ and a reducing agent, ____
At temperatures ABOVE the cardinal temperature of a bacterial species, the rate of cell division___; at temperatures BELOW that cardinal temperature, the rate of cell division___?
In the SIM test media, after a positive test, the H2S indicator was (soluble or insoluble) and (colored or colorless) and (intracellular or extra cellular)
Insoluble, colored, extracellular
Which set of phenol red carbohydrate fermentation test results shown would be most trusted and reliable?
PR- glucose + and PR - sucrose +
Where do the energy-producing steps of the carbohydrate fermentation take place?
Inside individual bacterial cells
Addition of 1000 microliters sample to 9.0 milliliters diluent is a ___ fold dilution
Addition of 100 microliters sample to 99.9 milliliters diluent is a ___ fold dilution
Which of the following is true regarding selective media?
Any/All of these answers can be correct
What is the fundamental, underlying reason why species of bacteria vary with respect to their abilities to ferment carbon sources
DNA - fermentation processes are catalyzed by genetically encoded enzymes
suppose you were concerned that a mistake had been made - you suspect that no chemcal indicator was included in your phenol red carbohydrate broth test media. which of the following could be a positive control?
add acid to your sample - make sure the color changes
Which of the following can be grown on properly prepared agar deeps?
facultative anaerobes, obligate aerobes, and strict anaerobes
which trait is most typical of an anaerobic species of bacteria
unable to convert hydrogen peroxide or superoxide radicals to less toxic molecules
which of the following is an indication that molecular oxygen is present
grown strictly aerobic species of bacteria
what is the selective media in mannitol salt agar
why do/did we incubate cCNA in a CO2 box?
An inoculated species of interest (streptococcus pneumonia) grows best in high CO2 environments
which of the following is responsible for the selectivity of cCNA agar?
colistin and naladixic acid
what does it mean when a medium is differential
it helps distinguish between species of bacteria
historically Streptococci spp. were grown in candle jars. which of the following is accurate regarding candle jar type environments
they have increased levels of carbon dioxide
which of the following is not accurate regarding candle jar environments
they have no oxygen present
the tests we use in this class for differentiation are
the tests we use in this class for differentiation of species directly examine
which of the following species would you expect to grow only under anaerobic conditions?
which of the following sugars was NOT included in our tSIA slants
If no growth was observed in a given phenol red carbohydrate test media after 48 hours, this fermentation test result
is considered unusable/ unreliable
suppose you were concerned that a mistake had been made, and no pH indicator was included in your urease test media, which of the following is a positive control you could use to test this media?
add base to the media- make sure the color changes
In the carbohydrate fermentation test broths, a positive result is recorded if the sample becomes more___>
MSA utilizes which pH indicator
A colony picked from __ plates should never be considered a pure culture
mannitol salt agar(MSA) cCNA, and HEA
which of the following results would be considered most conclusive / most reliable
which of the following species is a major cause of throat infections? (exhibits beta hemolysis, is DNAse positive, grows best with supplemental CO2)
H+ ions, H2S gas, 2,3 butanediol, and CO2 gas are each
possible products of carbohydrate fermentation
which of the following can cause false positives on a diagnostic test
low test specificity
which of the following can cause false negatives on a diagnostic test
low test sensitivity
what molecule is responsible for the color change that is observed in a positive citrate test
brom thymol blue
At pH 5.0, the indicator phenol red is which color?
If you were concerned that your DNAse assay was not working properly, which of the following could you perform as a positive control?
place DNA hydrolase on DNAse agar
historically some bacterial species were grown in candle jars. which of the following types of bacteria would not grow in candle jar type environments
which of the following processes are most likely to be performed by exoenzymes
digestion of polymers
which type of bacteria would be least likely to display oxidase and catalase activities?
strict anaerobic species
which type of media would be best to demonstrate isolation of a single species from a mixed species culture
all purpose media
what do PYR, oxidase, and dnase tests have in common
examine all levels of specific biochemical activities
the presence of indole is indicated by a ____ layer on top of a culture after addition of kovacs reagent
which explanation could account for a bacterial sample that is positive on each of the IMViC tests(++++) a set of tests designed to distinguish E.coli from E.aerogenes
the sample contains both E. coli and E. aerogenes
what characteristic do the enzymes that cut DNA, mannitol, and red blood cells have in common?
They are excreted proteins or exoenzymes
Recommended textbook explanations
Miller and Levine Biology
Joseph S. Levine, Kenneth R. Miller
Lehninger Principles of Biochemistry
David L Nelson, Michael M. Cox
Biocalculus: Calculus, Probability, and Statistics for the Life Sciences
Campbell Biology (AP Edition)
Cain, Jackson, Minorsky, Reece, Urry, Wasserman
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