Acrylate reductase of an anaerobic electron transport chain of the marine bacteriumShewanella woodyi

Abstract

Many microorganisms are capable of anaerobic respiration in the absence of oxygen, by using different organic compounds as terminal acceptors in electron transport chain. We identify here an anaerobic respiratory chain protein responsible for acrylate reduction in the marine bacteriumShewanella woodyi. When the periplasmic proteins ofS. woodyiwere separated by ion exchange chromatography, acrylate reductase activity copurified with an ArdA protein (Swoo_0275). Heterologous expression ofS. woodyi ardA gene (swoo_0275) inShewanella oneidensisMR-1 cells did not result in the appearance in them of periplasmic acrylate reductase activity, but such activity was detected when theardA gene was co-expressed with anardB gene (swoo_0276). Together, these genes encode flavocytochromecArdAB, which is thus responsible for acrylate reduction inS. woodyicells. ArdAB was highly specific for acrylate as substrate and reduced only methacrylate (at a 22-fold lower rate) among a series of other tested 2-enoates. In line with these findings, acrylate and methacrylate inducedardA gene expression inS. woodyiunder anaerobic conditions, which was accompanied by the appearance of periplasmic acrylate reductase activity. ArdAB-linked acrylate reduction supports dimethylsulfoniopropionate-dependent anaerobic respiration inS. woodyiand, possibly, other marine bacteria.