Physiological adaptations and tolerance towards higher concentration of selenite (Se(+4)) in Enterobacter sp. AR-4, Bacillus sp. AR-6 and Delftia tsuruhatensis AR-7.

Prakash, Dhan and Pandey, Janmejay and Tiwary, B N and Jain, R K (2010) Physiological adaptations and tolerance towards higher concentration of selenite (Se(+4)) in Enterobacter sp. AR-4, Bacillus sp. AR-6 and Delftia tsuruhatensis AR-7. Extremophiles : life under extreme conditions, 14 (3). pp. 261-72. ISSN 1433-4909

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Abstract

Environmental contamination with selenium is a major health concern. A few bacterial strains have been isolated that can transform toxic selenite to non-toxic elemental selenium only at low concentrations (0.001-150 mM) in recent past. We have previously reported isolation and characterization of few selenite-tolerant bacterial strains. These strains were found to be resistant to selenite at (300-600 mM) concentrations. In the present study we have characterized some physiological adaptations of strains Enterobacter sp. AR-4, Bacillus sp. AR-6 and Delftia tsuruhatensis AR-7 during exposure to higher concentration of selenite under aerobic and anaerobic environments. Adaptive responses are largely associated with alteration of cell morphology and change in total cellular fatty acid composition. Interestingly, electron microscopy studies revealed substantial decrease in cell size and intracellular deposition of Se(0) crystals when reduction is carried out under aerobic conditions. On the other hand, cell size increased with adhesion of Se(0) on cell surface during anaerobic reduction. Fatty acid composition analysis demonstrated selective increase in saturated and cyclic fatty acids and decrease in unsaturated ones during aerobic transformation. Changes observed during anaerobic transformation were in surprising contrast as indicated by total absence of saturated and cyclic fatty acids. Results presented here provide evidences for putative occurrence of two distinct mechanisms involved in tolerance towards higher concentrations of selenite utilization under aerobic and anaerobic conditions. Further, prior exposure to higher concentration of Se(+4) enabled rapid adaptation indicating role of inducible system in adaptation.

Item Type:	Article
Additional Information:	Copyright of this article belongs to Springer Science.
Uncontrolled Keywords:	Selenite � Toxicity � Tolerance �Physiological adaptations � FAMEs analysis �SEM and TEM
Subjects:	Q Science > QR Microbiology
Depositing User:	Dr. K.P.S.Sengar
Date Deposited:	08 Dec 2011 19:30
Last Modified:	03 Apr 2012 07:04
URI:	http://crdd.osdd.net/open/id/eprint/527

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