Int. j. Adv. Lif. Sci., Available online on at www. Int. J. Adv. Lif. Sci., Available online on at www. ijals.com Page 72 International Journal of Advanced Life Sciences (IJALS) ISSN 2277 – 758X Sridhar and Esther Joice, IJALS, Vol.3. May - 2012. RESEARCH ARTICLE Introduction Heavy metals are considered the most important form of pollution of the aquatic environment because of their toxicity and accumulation by organisms, such as fish (Emami Khansari et al., 2005). In recent years biochemical variables were used more when clinical diagnosis of physiology was applied to determine the effects of external stressors and toxic substances. Wepener (1997) suggested that haematology, biochemical changes, growth rate and oxygen consumption of fish be used in determining the toxicity of pollutants. Therefore, biochemical evaluations are gradually becoming a routine practice for determining health status of fish. Some species of fish used as biological indicators to detect the pollution range by metals (Ward and Neumann, 1999). Aquatic animals are frequently exposed to zinc-polluted waters (Everall et al., 1989b). Zinc has its primary effect on zinc-dependent enzymes that regulate RNA and DNA. Histopathological changes have been widely used as biomarkers in the evaluation of the health of fish exposed to contaminants, both in the laboratory (Wester and Canton, 1991; Thophon et al., 2003) and field studies (Hinton et al., 1992; Schwaiger et al., 1997 and Teh et al., 1997). One of the great advantages of using histopathological biomarkers in environmental monitoring is that this category of biomarkers allows examining specific target organs, including gills, kidney and liver, that are responsible Abstract Aquatic pollution has become global problem and is posing a serious threat to the survival of aquatic organisms. Persistent presence of pollutant like heavy metal in aquatic ecosystem has reportedly caused metabolic stress in organisms even to extent of mortality in some cases. The biochemistry and histology of tissues in the zinc treated Cyprinus carpio were heavily affected. The fishes treated with the probiotic bacteria Lactobacillus sporogenes increased in weight and gained more of protein, carbohydrate, lipids and enzymes. The possibility of utilization of this bacteria in aquaculture is discussed. Keywords: Lactobacillus sporogenes, Cyprinus carpio, protein, carbohydrate, lipids and zinc. Efficacy of probiotic bacteria Lactobacillus sporogenes on zinc toxicated fresh water fish Cyprinus carpio Sridhar, K* and P. Esther Joice PG & Research Department of Zoology, Government Arts College (Autonomous), Coimbatore- 641 018, Tamil Nadu, India. Email : srisridhar_1987@rediffmail.com Corresponding Author Sridhar, K PG & Research Department of Zoology, Government Arts College (Autonomous), Coimbatore- 641 018, Email: srisridhar_1987@rediffmail.com Article History Received on 18 April, 2012; Revised in revised form 22 April, 2012; Accepted 29 April, 2012