Transcriptional response of the obligate anaerobe Desulfuribacillus stibiiarsenatis MLFW-2T to growth on antimonate and other terminal electron acceptors.

Abstract

Enzymes of the dimethyl sulfoxide reductase (DMSOR) family catalyse two-electron redox reactions pivotal to the dissimilatory metabolism of a variety of organic and inorganic compounds. The draft genome of the obligately anaerobic bacterium Desulfuribacillus stibiiarsenatis MLFW-2T contains 14 genes that are predicted to encode catalytic subunits of DMSOR family enzymes. We quantified transcription of these genes during growth on antimonate, arsenate, nitrate and selenate, with the goal of identifying the respiratory antimonate reductase. Transcription of BHU72_10330, BHU72_03635 and BHU72_07355 was enhanced during growth on arsenate, nitrate and selenate, respectively, implicating these genes as encoding the catalytic subunits of a respiratory arsenate reductase (arrA), periplasmic nitrate reductase (napA) and membrane-bound selenate reductase (srdA) respectively. Transcription of BHU72_07145 increased markedly when MLFW-2T was grown on antimonate, suggesting that this gene encodes the catalytic subunit of a respiratory antimonate reductase, designated anrA. We also compared the transcriptomes of MLFW-2T during growth on antimonate and arsenate to examine the broader physiological response of the organism to growth on these substrates. Relative to arsenate, antimonate was found to induce transcription of genes involved in pathways for dealing with oxidative stress, including those involved in repairing damaged cellular biomolecules and scavenging reactive oxygen species.