Selenite reduction by Shewanella oneidensis MR-1 is mediated by fumarate reductase in periplasm

Abstract

In situ reduction of selenite to elemental selenium (Se(0)), by microorganisms in sediments and soils is an important process and greatly affects the environmental distribution and the biological effects of selenium. However, the mechanism behind such a biological process remains unrevealed yet. Here we use Shewanella oneidensis MR-1, a widely-distributed dissimilatory metal-reducing bacterium with a powerful and diverse respiration capability, to evaluate the involvement of anaerobic respiration system in the microbial selenite reduction. With mutants analysis, we identify fumarate reductase FccA as the terminal reductase of selenite in periplasm. Moreover, we find that such a reduction is dependent on central respiration c-type cytochrome CymA. In contrast, nitrate reductase, nitrite reductase, and the Mtr electron transfer pathway do not work as selenite reductases. These findings reveal a previously unrecognized role of anaerobic respiration reductases of S. oneidensis MR-1 in selenite reduction and geochemical cycles of selenium in sediments and soils.

Genomic, Proteomic, and Biochemical Analysis of the Organohalide Respiratory Pathway in Desulfitobacterium dehalogenans

“…A recent study on selenite reduction by Shewanella oneidensis MR-1 indicated that a deletion of cymA results in an inability to reduce selenite. Deleting the flavocytochrome c-encoding gene fccA led to lower selenite reduction rates, which seems to be in agreement with a role for flavocytochrome c as an electron shuttle, although it cannot be ruled out that FccA acts as the terminal selenite reductase (67). Methacrylate reduction in Geobacter sulfurreducens AM-1 was shown to be carried out by a periplasmic flavoprotein tetraheme cytochrome c complex (47).…”

Ecology and Biotechnology of Selenium-Respiring Bacteria

“…Interestingly, little reduction was observed using lactate as the electron donor, and no reduction at all was achieved using acetate or formate as the electron donor (53 reduction. Until now, detailed investigation of SeO 3 2Ϫ reduction via respiratory electron transport pathways was limited to a single study using S. oneidensis MR-1 (55). More details on the roles of respiratory reductases and the electron transport pathway in S. oneidensis MR-1 for SeO 3 2Ϫ reduction are described below.…”

“…9). Mutant strains defective in periplasmic terminal reductases, i.e., nitrate reductase (NapA), nitrite reductase (NrfA), and fumarate reductase (FccA), and periplasmic mediators of anaerobic respiration, i.e., MtrA and DmsE, were tested for SeO 3 2Ϫ reduction ability (55). The ⌬napA and ⌬nrfA mutant strains reduced selenite at the same rate as wild-type S. oneidensis MR-1.…”

Adsorption of zinc by biogenic elemental selenium nanoparticles

“…The reduction of selenite is reported to take place through dissimilatory respiration and the BioSeNPs are mainly formed in the periplasm or extracellularly [24,25]. Prior to batch adsorption experiments, BioSeNPs were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy -Energy Dispersive X-ray Spectroscopy analysis (SEM-EDXS), ζ-potential measurements and X-ray photoelectron spectroscopy (XPS).…”