Hugh Leifson Medium

 Principle

• Hugh Leifson Medium was formulated by Hugh and Leifson (1953), media is taxonomically significant for the fermentative and oxidative metabolism of carbohydrates in gram-negative bacteria. The media is composed of peptone, sodium chloride, dipotassium phosphate, glucose, bromothymol blue, and agar.
• Peptone provides nitrogen, carbon, and amino acids required for organism growth. Glucose serves as a carbon source. Sodium chloride maintains the osmotic equilibrium. Phosphate acts as a buffering agent.
• The bromothymol blue is a pH indicator. Less concentration of agar enables the determination of motility and aids in the distribution of acid throughout the tube produced at the surface of the medium.
• The high concentration of carbohydrate and low concentration of peptone avoid the possibility of an aerobic organism utilizing peptone and producing an alkaline condition help to neutralize slight acidity produced by an oxidative organism.
• Oxidative organisms produce acid in aerobic conditions with little or no growth and no acid formation. Whereas, fermentative organisms produce acid in both aerobic and anaerobic conditions. 
• The aerobic and anaerobic conditions are produced by sealing and unsealing the tubes. The bacterium capable of fermenting glucose produces yellow- or orange coloration. While the Non-fermenters will produce blue-green color.

 Use: Recommended by BIS for the isolation and cultivation of Vibrio cholerae and other Vibrio species which cause food poisoning and also used for differentiating between anaerobic and aerobic glucose fermenting bacteria.