New Scientific Status for Sulfate Reducing Bacteria

The Science

The pathway of electrons required for the reduction of sulfate in sulfate-reducing bacteria (SRB) is not yet fully characterized. In order to determine the role of a transmembrane protein complex suggested to be involved in this process, a deletion in Desulfovibrio vulgaris Hildenborough was created by marker exchange mutagenesis that eliminated four genes putatively encoding the QmoABC complex and a hypothetical protein (DVU0851). The Qmo (quinone-interacting membrane-bound oxidoreductase) complex is proposed to be responsible for transporting electrons to the dissimilatory adenosine-5′-phosphosulfate reductase in SRB. In support of the predicted role of this complex, the deletion mutant was unable to grow using sulfate as its sole electron acceptor with a range of electron donors. To explore a possible role for the hypothetical protein in sulfate reduction, a second mutant was constructed that had lost only the gene that codes for the DVU0851 protein. The second constructed mutant grew with sulfate as the sole electron acceptor; however, there was a lag that was not present with the wild-type or complemented strain. Neither deletion strain was significantly impaired for growth with sulfite or thiosulfate as the terminal electron acceptor. Complementation of the Δ(qmoABC-DVU0851) mutant with all four genes or only the qmoABC genes restored its ability to grow by sulfate respiration. These results confirmed the prediction that the Qmo complex is in the electron pathway for sulfate reduction and revealed that no other transmembrane complex could compensate when Qmo was lacking.


Sulfate reducing bacteria play important roles in the decomposition of organic matter and transformation of heavy metals in soils and subsurface environments. In the past five years, rapid progress has been made in advancing the status of sulfate reducer Desulfovibrio vulgaris to that of a model organism, enabling much more detailed studies on the central metabolic pathways of this class of microbes. Researchers at the University of Missouri have now identified a complex of electron transfer proteins, and the associated genes, in the D. vulgaris cell membrane that performs a critical step in sulfate reduction. This finding provides information on a central piece of the metabolic machinery that mediates sulfate reduction and will enable more refined studies of how these organisms adjust functional processes in response to environmental cues. This research has just been published in Applied and Environmental Microbiology and was conducted as a component of the collaborative ENIGMA Science Focus Area at Lawrence Berkeley National Laboratory.

Principal Investigator

Judy D. Wall
University of Missouri–Columbia


Zane, G. M., H. B. Yen, and J. D. Wall. 2010. “Effect of the Deletion of qmoABC and Promoter Distal Gene Encoding a Hypothetical Protein on Sulfate Reduction in Desulfovibrio vulgaris,” Applied and Environmental Microbiology 76. DOI:10.1128/AEM.00691-10.