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Micro Lab Practical 2

Terms in this set (142)

Source
Test tube that has the orginial culture of bacteria
Turbidity
cloudy broth due to bacteria
Viable count
Count of approximate number of living cells in a culture.
CFU/ (dilution factor x amount plated)
Calculation for viable count
isotonic
Solute concentration is equal inside and outside of the cell
exoenzyme
an enzyme made inside the cell and is secreted outside the cell and functions outside the cell.
target molecule
molecule that is broken down by exoenzyme in the media
selective media
media that contains chemicals that prevent growth of certain types of bacteria
zone of clearance
a "halo" that forms when an exoenzyme has destroyed a target molecule in the agar
media of starch test
starch agar
target molecule of starch test
starch (starch test)
product of hydrolysis of starch test
glucose (starch test)
exoenzyme of starch test
alpha-amylase
need to add this to a starch test to read the plate
iodine (starch test)
positive indicator of a starch test
zone of clearance (starch test)
media of lipase test
tributyrin agar
target molecule of lipase test
triglyceride
product of hydrolysis of lipase test
glycerol and 3 fatty acids
exoenzyme of lipase test
lipase
positive indicator of lipase test
zone of clearance (lipase test)
media of casein test
milk agar
target molecule of casein test
casein
product of hydrolysis of casein test
amino acids
exoenzyme of casein test
casease
positive indicator of casein test
zone of clearance (casein test)
media for blood hemolysis test
TSA 5% sheeps blood agar
target molecule of blood hemolysis test
red blood cell
3 exoenzymes of hemolysis test
alpha hemolysin = partial destruction of the red blood cell; beta hemolysin = complete destruction of red blood cell; gamma hemolysin = no destruction of red blood cell
3 positive indicators of blood hemolysis
alpha hemolysis = greenish tint to media; beta hemolysis = zone of clearance; gamma hemolysis = no change in media
media of gelatin test
gelatin deep
target molecule of gelatin test
gelatin
product of hydrolysis ofgelatin test
amino acids
exoenzyme of gelatin test
gelatinase
Special step needed before reading gelatin test
the gelatin test tude must be refrigerated before reading
positive indicator of gelatin test
liquid after refrigeration
the temperature at which gelatin agar melts
28'C
media of urea test
urea slant
target molecule of urea test
urea
product of hydrolysis of urea test
ammonium ions
exoenzyme of urea test
urease
pH indicator of urea test
phenol red (urea test)
Positive indicator of urea test
hot pink color of media
media of bile esculin test
bile eculin slant
ptarget molecule of bile esculin test
esculin
product of hydrolysis of esculin test
esculetin + glucose
exoenzyme of esculin test
glycosidase
special notes about bile esculin test
the media is selective and differential
positive indicator of bile esculin test
black color of media
differential
allows separation of one organism from a group based on some property of the organism
what is bile esculin selective for?
gram positive cocci (bile esculin)
what does the catalase test differentiate between?
aerobic and anaerobic organisms
exoenzyme of catalase test
catalase
target molecule of catalase test
hydrogen peroxide (H2O2)
what do we add to the catalase test
hydrogen peroxide (H2O2)
product of the catalse test
oxygen gas and water
positive result of catalase test
immediate formation of bubbles (oxygen gas)
in the catalase test, if an organism makes bubbles, is it aerobic or anaerobic
aerobic (catalase test)
what does the oxidase test differentiate between
gram negative rods of the anaerobic family Enterobacteriaceae and the aerobic family Pseudomonadaceae
exoenzyme of oxidase test
cytochrome c oxidase
reagent of oxidase test
oxidase reagent in oxidase strip
positive result of oxidase test
color change to blue/purple within 5 minutes
if you get a positive result in the oxidase test, is the organism aerobic of anaerobic?
aerobic (oxidase test)
what does the coagulase test differentiate between?
separates S. Aureus from other gram positive cocci
exoenzyme for coagulase test
coagulase
media for coagulase test
rabbit plasma test tube
positive coagulase test
clumping of media
why do we use a sterile plastic loop to inoculate the coagulase test?
a hot metal loop will denature the proteins and give a false negative
why do you not use a metal loop with the oxidase test?
metal oxidizes and if touched to the oxidase strip, it will give us a false positive.
what does the motility test differentiate between?
motile and nonmotile organisms
the media for the motility test
motility media
motility indicator
TTC
why does TTC turn red in the motility test?
TTC is the final electron acceptor for bacteria in the media. TTC is reduced by the addition of an election and turns red.
media of TSI test
multitest TSI media- Fermentation and sulfur reduction
enzyme of TSI test
sulfur reductase
target molecule of TSI test
sulfur (TSI test)
positive sulfur reduction result in TSI test
H2S visualized as FeS (black precipitate)
pH indicator in TSI test
phenol red (TSI test)
three sugars present in the TSI test
lactose, sucrose, glucose
in the TSI test, what is a positive indicator of fermentation?
yellow color with or without gas production (CO2)
what 2 tests does the TSI test?
1. fermentation 2. sulfur reduction
how we know if fermentation has produced a gas in an agar
the agar has cracks and fissures
strict anaerobe
an organism cannot grow and survive in the presence of oxygen. It lives by anaerobic metabolic mechanisms only.
facultative anaerobe
an organism that can live off aerobic or anaerobic metabolic mechanisms
cytochrome c oxidase
enzyme that is part of the electron transport chain in aerobic organisms
what is the reduced form of TTC
formazan
durham tube
small inverted test tube used to collect a gas in a broth
pH indicator of sugar fermentation test
phenol red (sugar fermentation)
three sugars tested in sugar fermentation tests
sucrose, lactose, glucose
strong acid positive for sugar fermentation test
yellow
basic positive for sugar fermentation test
pink
what are the IMViC reactions used to separate?
members of the anaerobic gram negative rod family Enterobacteriaceae into pathogens and normal flora.
media of indole test
tryptone broth
target molecule for indole test
tryptophan
product of hydrolysis of indole test
indole + pyruvate
exoenzyme of indole test
tryptophanase
reagent added for result for indole test
Kovac's
positive result of indole test
cherry red ring on top of broth after addition of Kovac's reagent
media of methyl red test
MR/VP broth
target molecule of methyl red test
glucose (MR)
product of fermentation of methyl red test
stable acid endproducts after fermentation of glucose
reagent added after incubation in methyl red
methyl red pH indicator
positive result of methyl red test
red color change after adding methyl red
media of vogues-proskauer test
MR/VP broth
target molecule of vogues-proskauer test
glucose (VP)
product of fermentation of vogues-proskauer test
the neutralized end product acetoin after fermentation of glucose
reagent added after incubation for vogues-proskauer test
Barritt's A and Barritt's B
positive result for vogues-proskauer test
reddish ring at top 1/4 of media
media of citrate test
citrate slant
target molecule of citrate test
citrate
product of metabolism in citrate test
basic endproducts
pH indicator of citrate test
Bromthymol Blue (BTB)
positive indicators of citrate test
heavy growth on slant and/or color change to blue
what enzymes (if any) are present if you see a gas bubble in the durham tube in the nitrogen respiration test
both nitrate reductase and nitrite reductase
what is the gas in the durham tube in nitrogen respiration
nitrogen gas (N2)
after incubation, if you do not have a gas bubble in the durham tube in the nitrogen respiration test, what is the next step?
add Nitrite A and Nitrite B
what does Nitrite A and Nitrite B test for the presence of? what is the color change?
the presence of nitrites. red color change.
if nitrites are present in nitrogen respiration, what enzyme was involved?
nitrate reductase
if no color change was seen after the addition of Nitrite A and Nitrite B, then what is the next step?
add zinc crystals
why do we add zinc crystals in the nitrogen respiration test? what color change do we expect to see?
zinc crystals test for the presence of nitrate (our starting material in the nitrogen respiration test). if nitrate is present the zinc crystals will turn the broth red.
if zinc crystals turn the broth red in the nitrogen respiration test, what do we know about the enzymes?
there are no exoenzymes
what is the mannitol salt test selective for and what is it differential for
mannitol salt test is selective for organisms that can grow in the presence of a high salt environment and is differential for organisms that can ferment mannitol.
what is the pH indicator for the mannitol salt test?
phenol red (mannitol salt)
what is the positive indicator for the mannitol salt test
yellow growth on the media AND yellow media
what is a negative indicator for the mannitol salt test
no growth (organism is not salt tolerant), or growth without a yellow halo (no fermentation)
what is the percentage of sodium chloride in the mannitol salt test?
7.5% sodium chloride
what does the mannitol salt test differentiate between?
pathogenic and non-pathogenic Staphylococci. Pathogenic Staphylococci grows and ferments mannitol. Non-pathogenic Staphylococci can grow, but don't cause a color change (doesn't ferment mannitol).
what is the exoenzyme of the mannitol salt test?
mannitol dehydrogenase
how many chambers doe the Enterotube have?
12 chambers
how many tests does the Enterotube use?
15 tests
what two sugars are in the Eosin Methylene Blue agar?
lactose and sucrose
what two dyes are in the Eosin Methylene Blue agar?
Eosin Y dye and methlyene blue dye
what is the EMB test selective for?
gram negative enteric rod growth
what is a positive indicator for a strong fermenter in the EMB?
dark purple with a green metallic sheen for vigorous fermenters
what is a positive indicator for a weak fermenter in the EMB test?
pink coloration to the colony
what is the purpose of the Hektoen Enteric Agar?
to isolate Salmonella and Shigella from other gram negative enterics
what three sugars are in the HE test?
sucrose, lactose, and salicin
besides sugar fermentation, what else is tested for in the HE test?
sulfur reduction (which shows as a black precipitate)
what is a positive indicator for the HE test
yellow orange growth and media for fermentation, and black precipitate for sulfur reduction.
MacConkey test is selective for what?
gram negative enteric rods
what is the pH indicator of the MacConkey test?
neutral red dye
what is a positive result of the MacConkey test?
hot pink colony and hot pink media
what is a negative result for the MacConkey test?
no color in media or beige-tan media
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