Enzyme Producing Bacteria in the Gastrointestinal Tracts of Labeo rohita (Hamilton) and Channa punctatus (Bloch)

Fish receive bacteria in the digestive tract from the aquatic environment through water and food that are populated with bacteria. Being rich in nutrient, the environment of the digestive tract of fish confers a favourable culture environment for the microorganisms. The importance of intestinal bacteria in the nutrition and well–being of their hosts has been established for homeothermic species, such as birds and mammals (Floch et al., 1970). However, there is limited information for fish, the poikilothermic vertebrates. Though the digestive tract of endotherm that is mainly colonized by obligate anaerobes (Finegold et al., 1983), the predominant bacterial species isolated from most of the fish digestive tracts have been reported to be aerobes or facultative anaerobes (Trust and Sparrow, 1974; Bairagi et al., 2002; Saha et al., 2006). Endogenous digestive enzymes in fish have been studied by several workers (Dhage, 1968; Kawai and Ikeda, 1972; Das and Tripathi, 1991). However, information regarding the enzyme producing intestinal bacteria, their source and significance in fish is scarce. In the present study, an attempt has been made to investigate the relative amount of protease, amylase and cellulase producing bacteria in the gastrointestinal (GI) tracts of two fresh water teleosts, namely the Indian major carp rohu, Labeo rohita (Hamilton) and the murrel, Channa punctatus (Bloch). Further, intestinal isolates were evaluated for extracellular enzyme producing capacities. Data suggest that the composition of the specific enzyme producing bacterial flora in the fish digestive tracts may have correlation with their feeding habits.