TRYPTONE LACTOSE IRON AGAR

Tryptone Agar was developed by Vera for the accurate differentiation and identification of aerobes and anaerobes by means of motility and fermentation reactions. Tryptone Lactose Iron Agar medium is recommended to study motility of organism and simultaneous sulphite reduction in acidic environment. Due to presence of phenol red in the medium, on fermentation of lactose the medium turns yellow due to production of acid and gas. The ability of an organism to produce H2S is a consistent characteristics and an H2S producer usually produce gas (CO2 + H2) in carbohydrate media which is visualized as air bubbles in the medium.
H2S production takes place in the presence of R1-SH group provided by cystine present in casein enzymic hydrolysate or through reduction of an inorganic sulphur source such as thiosulphate. H2S is a colourless gas, which upon contact with ferrous salt produces ferrous sulphide, a black precipitate indicated by a visible black reaction. Sodium sulphite at a concentration less than 0.05% is not inhibitory to Clostridium sporogenes.

for identi?cation of anaerobes on the basis of motility, hydrogen sulphide production and lactose fermentation