Aerobic Reduction of Chromium(VI) by Pseudomonas corrugata 28: Influence of Metabolism and Fate of Reduced Chromium

Abstract

Pseudomonas corrugata 28 represents a microorganism that can potentially be applied for in situ bioremediation of Cr(VI) contaminated sites. This strain combines a high resistance toward toxic Cr(VI) with the ability to reduce Cr(VI) to Cr(III) under oxic conditions. In this study, the aerobic reduction of Cr(VI) by Pseudomonas corrugata 28 was examined under different carbon and sulfur supply conditions to assess the influence of microbial carbon and sulfur metabolism on Cr(VI) reduction. The fate of reduced chromium was elucidated by investigating the speciation of chromium in solution as well as the interaction of chromium with bacterial surfaces. Reduction of Cr(VI) was found to be a metabolic process resulting mainly in the formation of dissolved organic Cr(III)-complexes. Small amounts of reduced chromium were weakly associated with bacterial surfaces. The formation of inorganic Cr(III)-precipitates was not indicated.

Keywords:

• hexavalent chromium
• microbial reduction
• aerobic conditions
• organic metal complexes
• scanning transmission X-ray microscopy (STXM)
• Pseudomonas corrugata 28

Acknowledgments

The X-ray microscopy studies were conducted at the STXM beamlines X07D (PolLux), SLS, Paul Scherrer Institute, Villigen, Switzerland and X-1A, NSLS, Brookhaven National Laboratory, Upton/NY, USA. The development of the X-ray microscopes at SLS and NSLS was financially supported by BMBF, Germany under project 05 KS4 WE1/6 as well as the Office of Biological and Environmental Research, U.S. DoE under contract DE-FG02-89ER60858 and the NSF under grant DBI-9605045, respectively. We are deeply grateful to George Tzvetkov and Sue Wirick for their help at the beamlines.