Background to the study

Probiotic bacteria are essential for beneficial effect on particular organism’s health and host nutrition for healthy gastrointestinal function. The action of intestinal flora results in vital benefits, including protection against pathogens and development of immune system. Probiotics are defined as “a live microbial adjunct which has a beneficial effect on the host by modifying the host associated or ambient microbial community, by ensuring improved use of the feed or enhancing its nutritional value, by enhancing

the host response towards disease, or by improving the quality of its ambient environment” Verschuere et al. (2000). Probiotics are also regarded as an environmentally friendly treatment method

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 digestive tract of fish confers a favorable culture environment for the microorganisms.

The gastrointestinal tract of fish is a complex ecosystem possessing a specific micro-biota consisting of aerobic, facultative anaerobic and obligate anaerobic bacteria (Gomez and Balcazar, 2008).

The predominant bacterial species isolated from most of the fish digestive tracts have been reported to be aerobes or facultative anaerobes (Bairagi et al., 2002; Saha et al., 2006). The isolated many lactic acid bacteria are proved to function as probiotics, which are benefit to host health, when ingested in sufficient quantities. The colonization of the gut by probiotic bacteria prevents growth of harmful bacteria by competition exclusion and by the production of organic acid and antimicrobial compounds.

Statement of problem

The acid and bile tolerance as well as two fundamental properties that indicate the ability of probiotic microorganism to survive the passage though the upper gastrointestinal tract, particularly acidic condition in the stomach and the presence of bile in the small intestine (Hyronimus et al., 2000; Erkkila and Petaja, 2000). Although lactic acid bacteria were not dominant population in fish, it has been well documented in several investigations that lactic acid bacteria are a part of the native microbiota of aquatic animals from temperate regions (Ringo, 2004).

All reports pointed out on the presence of probiotic bacteria from freshwater fish gills, gut, tissue and liver, when artificial feed supplementation of fresh water forms, but dam environment, fresh water fish gut bacteria was analyzed fewer. So, in the present study revealed that Isolation, enumeration and identification of probiotic bacteria from Kaingi dam located in Niger state.