Chromate reduction by Burkholderia cepacia MCMB-821,isolated from the pristine habitat of alkaline crater lake

The Cr(VI)-reducing bacterial strain MCMB-821 was isolated from the alkaline crater lake of Lonar and was identified as Burkholderia cepacia. MCMB-821 was resistant to 1,000-ppm Cr(VI) and reduced 98% of the 75 ppm Cr(VI) within 36 h at pH 9.0 in the presence of 2% salt and lactose as the electron donor. The chromate-reducing efficiency of MCMB-821 was comparable under both aerobic as well as anaerobic conditions. Electron paramagnetic resonance spectroscopy data suggested that MCMB-821 reduced Cr(VI) to Cr(III) via the formation of transient Cr(V) intermediate. The chromate-reducing ability of MCMB-821 was suppressed in the presence of membrane inhibitors and enhanced in the presence of 2,4-dinitrophenol, suggesting the involvement of electron transport chain in the Cr(VI) bioreduction.