Hugh Leifson Medium

This medium is used to determine the fermentation of carbohydrates (glucose) under aerobic and anaerobic conditions.

Composition

Ingredients

gram / liter

Peptic digest of animal tissue

Sodium chloride

Potassium hydrogen phosphate

Glucose

Bromothymil purple

Agar-agar

The final pH value (at 25 ° C) is 6.8 ± 0.2 2.00

5.00

0.30

10.00

0.05

2.00

** The composition is verified and brought to the necessary parameters

Preparation:

Stir 19.4 g of powder in 1000 ml of distilled water. Warm up with frequent stirring, boil for complete dissolution of the particles. Pour into two test tubes (for fermentation in aerobic and anaerobic conditions). Sterilize by autoclaving at 1.1 atm (121 ° C) for 15 min. Cool tubes in an upright position.

Principle and evaluation of the result:

This Wednesday was suggested by Hugh and Leifson (1). They described the taxonomic significance of the enzymatic and oxidative metabolism of carbohydrates for gram-negative intestinal bacteria.

The medium contains a high concentration of carbohydrate and a low concentration of peptic digest of animal tissue so that the amines formed during the fermentation of peptone can not neutralize the acid, which, for example, is formed in small amounts during the oxidation of the carbohydrate (2). Phosphate imparts buffer properties to the medium. The concentration of agar-agar allows to determine the mobility of microorganisms and promotes the propagation of acid in the medium. Microorganisms oxidizing the carbohydrate produce acid under aerobic conditions, while in anaerobic they do not grow and do not form an acid, while fermenters form acid in both test tubes (under aerobic and anaerobic conditions).

Acidity of the medium:

At 25 ° C, the aqueous solution (1.94% w / v) has a pH of 6.8 ± 0.2.