Microbiology 2117 Lab Finals Sample Questions
and Answers 100% Correct
How is the TSI test inoculated?
Stab and streak w/ needle
What is a red TSI test with black sediment indicative of?
(-) sugar fermentation, (+) H2S production
What would a gama-hemolytic result look like in a blood hemolysis test?
No visible change in media
What is a medium that would be differential?
Blood agar
What is the difference of selective and differential media?
Selective media inhibits one group of microbes while promoting the growth of another.
Differential media discriminates between closely related organisms.
What is the pH indicator in the TSI test?
Phenol red
What type of bacteria grows on mannitol salt agar?
Gram (+) cocci
What does a positive mannitol salt test look like?
Yellow agar with a clear space around the colonies
, What causes the mannitol salt agar to turn yellow?
The sugar mannitol was fermented and acids produced.
What is the pH of a yellow Urease test?
It is the same acidity as it was before innoculation
A green citrate test would be?
Negative
A green citrate test would indicate what change in pH?
No change to pH occurred
What is the pH indicator used in the citrate test?
Bromothymol blue
What is a test you can use to identify Gram (-) colonies?
Indole test
What color does iodine turn when it is combined with starch?
Brown
Which test contains the amino acid tryptophan?
Indole test
In egg yolk media, what would a streak of bacteria with a white fluffy border indicate?
Egg yolk has been broken down, positive for lecithinase
and Answers 100% Correct
How is the TSI test inoculated?
Stab and streak w/ needle
What is a red TSI test with black sediment indicative of?
(-) sugar fermentation, (+) H2S production
What would a gama-hemolytic result look like in a blood hemolysis test?
No visible change in media
What is a medium that would be differential?
Blood agar
What is the difference of selective and differential media?
Selective media inhibits one group of microbes while promoting the growth of another.
Differential media discriminates between closely related organisms.
What is the pH indicator in the TSI test?
Phenol red
What type of bacteria grows on mannitol salt agar?
Gram (+) cocci
What does a positive mannitol salt test look like?
Yellow agar with a clear space around the colonies
, What causes the mannitol salt agar to turn yellow?
The sugar mannitol was fermented and acids produced.
What is the pH of a yellow Urease test?
It is the same acidity as it was before innoculation
A green citrate test would be?
Negative
A green citrate test would indicate what change in pH?
No change to pH occurred
What is the pH indicator used in the citrate test?
Bromothymol blue
What is a test you can use to identify Gram (-) colonies?
Indole test
What color does iodine turn when it is combined with starch?
Brown
Which test contains the amino acid tryptophan?
Indole test
In egg yolk media, what would a streak of bacteria with a white fluffy border indicate?
Egg yolk has been broken down, positive for lecithinase
