YEAST EXTRACT AGAR (as per ISO) is used for plate count of microorganisms in water. Yeast Extract and Tryptone and Yeast extract provide sources of nitrogen, amino acids, essential vitamins, and carbon required for organism growth. Agar is the solidifying agent. In nature, all water contains some impurities. As we know that microbial pathogens are often found in water frequently as a result of fecal matter from sewage discharges, leaking septic tanks, or runoff from animal feedlots. As water flows in streams, sits in lakes, and filters through layers of soil and rock in the ground, it dissolves or absorbs the substances that it touches. The combination of media ingredients and the appropriate incubation temperature of 35°C and 22°C allow the detection of a large number of microbial contaminants. Inoculate the culture medium by the pour-plate method or by spreading the material on the surface. Incubation period can extend up to 7 days also at 28 °C aerobically.