The sugar fermentation test is the most commonly used biochemical reaction and is particularly important in the identification of intestinal bacteria. The vast majority of bacteria can utilize sugars as a carbon and energy source, but they vary greatly in their ability to break down sugars. Some bacteria can break down certain sugars and produce acid and gas; others produce only acid and no gas. Example

Operation method

Sugar fermentation measurement experiment

Principle

Acid production can be determined using indicators. Bromocresol violet [pH 5.2 (yellow) to 6.8 (purple)] is added in advance to the preparation of the medium, which causes the medium to change from purple to yellow when the fermentation produces acid. Gas production can be demonstrated by the presence or absence of bubbles in the inverted DeHaan's tubules in the fermentation tube.

Materials and Instruments

Escherichia coli Proteus vulgaris
Glucose fermentation medium Lactose fermentation medium
Test tubes Test tube racks Inoculation rings

Move

1. Numbering: Use a marker to label each test tube with the name of the fermentation medium and the name of the bacteria inoculated.
2. Inoculation: Take 3 test tubes containing glucose fermentation medium, inoculate 1 tube with E. coli according to the number, inoculate the other tube with Proteus mirabilis and leave the third tube uninoculated as a control. Take 3 test tubes with lactose fermentation medium, inoculate 1 tube with E. coli, 1 tube with Aspergillus oryzae, and the third tube without inoculation as control.
3. The above inoculated glucose and lactose fermentation tubes and control tubes are incubated in a greenhouse at 37°C for 24 hours.
4. Observations.5. Enter the results of the experiment in the table below. "" means acid and gas production; "+" means acid and no gas production; "-" means no acid and no gas production.

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