Sowmya ET AL., HALOPHILIC METAL TOLERANT BACTERIA……..

Sowmya M.*, Rejula M. P*. and Mohamed Hatha A.A, Halophilic Metal Tolerant Bacteria from Vembanad Lake as Possible means of Bioremediation of Lead and Cadmium, (Ed.) S.Jisha, B.Hari & T.K.Remesan, Proc. Nat. Sem. on Env. Biotech. Chall. and Oppor.,  Envirotech-2008, P.G. Dept. of Zoology, S.N.C. Natiika, pp63-63

Sowmya M.*, Rejula M. P*. and Mohamed Hatha A.A. # *School of Environmental Sciences, M.G. University, Priya Darsini Hills., Kottayam. #Department of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, CUSAT, Cochin

Abstract Man, being at the top of the food chain, is at greater risk of suffering from health hazards associated with toxic metals because of bioaccumulation/ biomagnification. Sediment is the ultimate depository of many chemical compounds including heavy metals from natural and anthropogenic sources. Because of their highly diverse metabolic and physiological capabilities, microorganisms are capable of resisting high concentrations of toxic heavy metals/ xenobiotics in their environment and are often considered as effective tools of bioremediation of polluted environments. In the present study sediment samples from Vembanad Lake – the largest lagoon backwater system on the southwest coast of India – were screened for the presence of halophilic bacteria that are tolerant to heavy metals. A total of 35 bacterial strains belonging to different genera such as Alcaligenes, Vibrio, Kurthia, Staphylococcus and members of the family Enterobacteriaceae were isolated from 21 sediment samples during February to April, 2008. The salt tolerance and optimum salt concentrations of the isolates revealed that most of them were moderate halophiles followed by halotolerant and extremely halotolerant groups. The Minimum Inhibitory Concentrations (MICs) against cadmium and lead for each isolate were determined. The isolates showed higher MIC against lead than cadmium. Based on the resistance limit concentration most of them were more tolerant to lead than cadmium at all the three salt concentrations tested. Metal reduction efficiency of selected isolates was also carried out. Isolates showed a maximum reduction efficiency of 37% and 99% against cadmium and lead respectively. The study reveals the future prospects of halophilic microorganisms in the field of bioremediation. The findings also disclose the vast treasure of unexplored microbial diversity of this Ramsar site.