COOKED ROSE BENGAL AGAR BASE

Description

Cooke Rose Bengal Agar is a selective medium formulated as per Cooke. A variety of inhibitory agents have been used to inhibit bacteria in an attempt to isolate fungi from mixed flora. The Kingdom Fungi includes some of the most important organisms, both in terms of their ecological and economic roles. By breaking down dead organic material into simpler forms, they continue the cycle of elements through ecosystems. In addition, most vascular plants could not grow without a symbiotic association with fungi, or mycorrhizae, that inhabit their roots and supply essential nutrients. Other fungi provide numerous drugs (such as penicillin and other antibiotics), foods like mushrooms, truffles and morels, and the bubbles in bread, champagne, and beer. Waksman described an acid medium consisting of peptone, dextrose, inorganic salts and agar for the isolation of fungi from soil. Cooke used the Waksman medium without adjustment for isolation of fungi from sewage. It was discovered that papaic digest of soyabean meal was particularly suitable for use in this medium and that the combination of chlortetracycline, or oxytetracycline, with rose bengal increased the selectivity of the medium. Smith and Dawson used rose bengal for the inhibition of bacteria in media which has almost neutral reaction concerned with retardation of the development of fungi. Martin used 1: 30,000 Rose bengal and 30?g Streptomycin per ml and found that a wide variety of bacteria are inhibited at reactions between pH 5.5 to 6.5 without inhibiting fungi. The medium should not be exposed to light as photo-degradation of rose bengal yields compounds that are toxic to fungi. Microscopic examination coupled with biochemical testing using pure cultures is recommended for complete identification. Due to the selective properties of this medium and the type of specimen being cultured, some strains of fungi may be encountered that fail to grow or grow poorly on the complete medium; similarly, some strains of bacteria may be encountered that are not inhibited or partially inhibited.