14: Fermentation Flashcards
Used to detect acid and gas production from carbohydrates
Fermentation tube
Fermentation medium contains:
Peptone, an acid-base indicator (phenol red), an inverted tube to trap gas, and 0.5-1.0% of the desired carbohydrate
Phenol red indicator is red (neutral) in an inoculated fermentation tube, fermentation that results in acid production will turn what color?
Yellow (pH 6.8 or below)
If gas is produced during fermentation it will be trapped in the inverted, or _____, tube
Durham
During prolonged incubation periods (greater than 24 hrs.) many bacteria grow oxidatively on the peptone after exhausting the carbohydrate supplied, what does this result in?
Neutralization of the indicator turning it red b/c of ammonia production
Used to distinguish organisms that produce large amounts of acid from glucose and organisms that produce the neutral product acetoin.
MRVP broth
A glucose-supplemented nutrient broth used for the methyl red (MR) test and the Vogues-Proskauer (V-P) test
MRVP medium
If an organism produces a large amount of organic acid from glucose, the medium will be what color?
remain red, indicating a pH below 4.4
Methyl red is orange-red between….
pH 4.4 and 6.0
If neutral products are produced methyl red will turn _____, indicating a pH above 6.0
yellow
The production of acetoin is detected by the addition of:
potassium hydroxide & α-naphthol
If accetoin is present, the upper part of the medium will turn red; a negative V-P test will turn the medium _____
light brown
Which medium is selctive?
Citrate agar
Bacteria with the enzyme citrate lyase can break down citrate to form _____, which can be reduced in fermentation.
pyruvate
What happens when bacteria use citrate and ammonium?
the medium is alkalized b/c of ammonia
