Lab 16 - Fermentation Flashcards
for each metabolic test, what should we know?
- The test name
- What you are specifically testing for
- The medium or substrates and any reagants used
- A positive vs. negative test results
- The reason for a positive result
what is the OF glucose?
it is a medium containing glucose
what is the question we are trying to answer for OF glucose?
Is the unknown bacteria/organism oxidative (carrying out respiration) or fermentation (carrying out fermentation)?
what does the OF medium contain?
-Glucose (it will use glucose for either respiration or fermentation).
-Peptides
-Bromothymol blue (a pH indicator)
what does Bromothymol blue indicate for each color? (in OF glucose medium)
yellow = acidic
green = neutral
blue = basic
if the color in OF glucose is yellow, what does that mean?
it means that it is metabolizing sugar and therefore fermentation is happening
when testing an organism in OF glucose, two tubes are inoculated. What are those two tubes?
1 open to the air (aerobic conditions)
and 1 covered with mineral oil (anaerobic conditions)
Organisms capable of fermentation of the sugar will grow in the anaerobic areas, making the anaerobic portion of the medium what?
Making it acidic and yellow
Organisms that can metabolize the sugar in the presence of oxygen turn the medium into what?
acidic in the open tube
in an OF glucose medium, what does the oxygen make a difference in whether it’s present or not?
When oxygen is present, the process is called oxidation, and when oxygen is absent it is called fermentation. This test provides insight into the ability of the bacterium to use glucose by both methods.
in the results of OF, if the covered tube is yellow, what does that mean?
that means the bacteria is fermenting glucose and making acids
in the results of OF, if the entire open tube is yellow, what does that mean?
that means that the bacteria is either using glucose via respiration or fermentation
in the results of OF, if the top portion of the open tube is yellow, what does that mean?
that means the bacteria is using glucose via respiration
in the results of OF, if the tube is blue, what does that mean?
that the bacteria are using peptides to make basic products
For the following bacterial species, decide whether they are oxidative or fermentation:
-E. coli:
Open tube - yellow
Covered tube - yellow
Fermentative; since both tubes are yellow. In the open tube, we aren’t able to decide whether it is oxidative or fermentation, but since they were both yellow, we can say that they are fermentative.
For the following bacterial species, decide whether it is oxidative or fermentation:
-P. aeruginosa:
Open tube - yellow on the top, green at the bottom.
Covered tube - green
Oxidative
For the following bacterial species, decide whether it is oxidative or fermentation:
-A. faecalis:
Open tube - blue
Covered tube - blue
Non-saccharolytic
For the following bacterial species, decide whether it is oxidative or fermentation:
- C. freundi:
Open tube - yellow
Covered tube - yellow
fermentative
what is the question we are trying to figure out in MRVP?
Is the organism performing mixed acid or butanediol fermentation?
what does the MRVP O-F medium contain?
glucose
peptides
what is the mixed acid fermentation test?
The organisms ferment glucose and make lots of acids that make methyl red, red. We add methyl red to see if it is a positive mixed acid or negative.
acids ____ the pH of a medium
lower
what is a positive test for mixed acid fermentation?
Red
(pH < 4.5)
what is a negative test for mixed acid fermentation?
-Orange at in-between pH
and/or
-Yellow at pH > 5.5
what is Butanediol fermentation?
when glucose is broken down and we get a red color again. We add VP reagent A and B to see if it is red.
what is the question for the citrate utilization test?
can bacterium use citrate as the sole C-source?
what organisms in the citrate test can transport and utilize citrate?
only organisms that have citrate permease
What does Simmon’s citrate agar contain?
-Sodium citrate: the sole source of Carbon.
-Bromothymol blue (the pH indicator).
what do the pHs indicate in the citrate utilization test?
Green at pH 6.9
Blue at pH 7.6
If the bacteria can transport and use citrate, what do they produce?
they produce alkaline products like sodium carbonate and ammonia, so the color changes to blue
what is a positive citrate test?
blue
what is a negative citrate test?
green
