Topic 14: Fermentation of Carbohydrates

bacterium

Once a(n) ________ has been determined to be fermentative by the OF test, further tests can determine which carbohydrates are fermented.

Fermentation

________ medium containts peptone, phenol red, and inverted tube to trap gas.

Monosaccharide

glucose

Disaccharide

sucrose

Polysaccharide

cellulose

Prolonged incubation periods (more than 24 hrs), bacteria will grow oxidatively on the peptone after exhausting carbohydrate supply

causing neutralization of indicator (red)

If organism produces a large amount of organic acid from glucose

medium remains red when methyl red is added in a + MR test indicating pH is below 4.4

If neutral products produced

will turn yellow indicating pH is above 6.0

if present

upper part of medium will turn red

What is an example of a monosaccharide?

glucose

What is an example of a disaccharide?

sucrose

What is an example of a polysaccharide?

cellulose

What is used to detect acid and gas production from carbohydrates?

fermentation tube

What does a fermentation medium/tube contain?

peptone, phenol red, and inverted tube to trap gas

What traps gas in a fermentation tube?

durham tube

Can fermentation occur with or without oxygen present?

Both

Why does prolonged incubation periods (more than 24 hrs) give a false result for fermentation tube?

bacteria will grow oxidatively on the peptone after exhausting carbohydrate supply causing neutralization of indicator (turns red)

What test is used to distinguish between organisms that produce large amounts of acid from glucose and those that produce neutral product acetoin?

MRVP test

Production of acetoin is dependent on ___.

length of incubation