Revealing Pathways that Drive Metabolism in Sulfate-Reducing Bacteria


Sulfate-reducing bacteria (SRB), commonly found in oxygen-deprived habitats, are known for their involvement in the corrosion of metals and the formation of toxic sulfide; however, they also are involved in controlling the transformations and transport of a number of toxic metal contaminants in soils and groundwater. Effective use of SRBs to control metal contaminants requires a better understanding of their bioenergetic pathways for sulfate reduction. A team of scientists from the University of Missouri, Oak Ridge National Laboratory, and Environmental Molecular Sciences Laboratory (EMSL) used a mutant form of an SRB, Desulfovibrio alaskensis, to test the hypothesis that the sulfate reduction that occurs in the cell’s interior cytoplasm relies on a flow of electrons from the cell’s periplasm, found between the cell’s two exterior membranes. The researchers characterized bacterial growth and examined gene expression using proteomic and transcriptomic analyses at EMSL. Their results indicate that a protein that spans the inner membrane from the periplasm to the cytoplasm and another protein found only in the periplasm are essential for transferring electrons from the periplasm to the cytoplasm to drive sulfate reduction. These research results also are consistent with another recently discovered biochemical pathway involving hydrogen cycling that increases the efficiency of energy use in many SRBs. Together, these findings could be important in designing pathways for biofuels production.


Reference: Keller, K. L., B. J. Rapp-Giles, E. S. Semkiw, I. Porat, S. D. Brown, and J. D. Wall. 2014. “A New Model for Electron Flow for Sulfate Reduction in Desulfovibrio alaskensis G20,” Applied and Environmental Microbiology 80(3), 855-68. DOI:10.1128/AEM.02963-13.