Isolation and characterization of Cr6+ reducing bacteria and their potential use in bioremediation of chromium containing wastewater

In this paper the ability of bacillus pumilus,alcaligenes faecalis and staphylococcus sp. to reduce cr6+ into cr3+ was evaluated. b. pumilus could tolerate cr6+ up to 2 mg/ml. a. faecalis and staphylococcus sp. resisted cr6+ up to 1.4 and 1.6 mg/ml,respectively. b. pumilus and staphylococcus sp. showed optimum growth at ph 8 while a. faecalis showed maximum growth at ph 7. all bacterial strains showed optimum growth at 37°c. b. pumilus was found sensitive against amoxicillin and tetracycline while found least sensitive against polymyxin b. a. faecalis was found sensitive to tetracycline while showed least sensitivity against amoxicillin. staphylococcus sp. showed high sensitivity against vancomycin while minimum against erythromycin. all bacterial strains showed different degrees of sensitivity against to kanamycin,erythromycin,streptomycin,oxytetracyclin and neomycin but all bacterial strains showed resistance against bacitracin. b. pumilus showed 95%,a. faecalis showed 97% and staphylococcus sp. showed 91% ability to reduce cr6+ into cr3+ within 24 hours from the medium containing 100 μg cr6+/ml. bacterial strains can be exploited for bioremediation of hexavalent chromium containing wastes,since they seem to have potential to reduce the toxic hexavalent form to its nontoxic trivalent form. copyright 2010 zoological society of pakistan.