m-Endo Agar LES, Dehydrated 500 g

For customer preparation of microbiological media. m-Endo LES is a selective and differential medium used to enumerate total coliform bacteria in water, wastewater, and food samples using the membrane filtration technique. The formulation promotes growth of Gram-negative organisms while inhibiting Gram-positive bacteria, and differentiates coliforms by their typical appearance: red colonies with a golden-green metallic sheen. Selectivity is provided by deoxycholate and lauryl sulfate; lactose serves as the fermentable carbohydrate; peptones and yeast extract supply essential nutrients; and basic fuchsin functions as the indicator system. Lactose-fermenting organisms produce acetaldehyde, which reacts with basic fuchsin and sodium sulfite to produce a red zone around colonies and, in coliforms, the characteristic metallic sheen (heavy inocula may suppress sheen formation). Non-lactose fermenters form clear, colorless colonies.