Bacterial respiration of arsenic and selenium

Abstract

Oxyanions of arsenic and selenium can be used in microbial anaerobic respiration as terminal electron acceptors. The detection of arsenate and selenate respiring bacteria in numerous pristine and contaminated environments and their rapid appearance in enrichment culture suggest that they are widespread and metabolically active in nature. Although the bacterial species that have been isolated and characterized are still few in number, they are scattered throughout the bacterial domain and include Gram-positive bacteria, beta, gamma and epsilon Proteobacteria and the sole member of a deeply branching lineage of the bacteria, Chrysiogenes arsenatus. The oxidation of a number of organic substrates (i.e. acetate, lactate, pyruvate, glycerol, ethanol) or hydrogen can be coupled to the reduction of arsenate and selenate, but the actual donor used varies from species to species. Both periplasmic and membrane-associated arsenate and selenate reductases have been characterized. Although the number of subunits and molecular masses differs, they all contain molybdenum. The extent of the environmental impact on the transformation and mobilization of arsenic and selenium by microbial dissimilatory processes is only now being fully appreciated.

Metagenomic analysis revealed highly diverse microbial arsenic metabolism genes in paddy soils with low-arsenic contents

“…strain PHS-1 (Kulp et al, 2008;Zargar et al, 2010), which was suggested to be conducted by a new arsenite oxidase clade, ArxA (Zargar et al, 2012), though no information is presently known on the this enzyme's functioning (van Lis et al, 2013). Through these processes, As speciation and bioavailability are altered, affecting its toxicity, environmental behavior and fate in the environment, and also its accumulation into food crops (such as rice) (Jia et al, 2014(Jia et al, , 2013Stolz and Oremland, 1999).…”

Biosynthesis and structural characteristics of selenium nanoparticles by Pseudomonas alcaliphila

“…Gurunathan nanoparticles by Bacillus subtilis [19]. To date, about 16 diverse species of bacteria and Arechaea have been discovered to reduce selenium oxyanions to the red, amorphous or monoclinic allotropes of Se 0 [20,21].…”

Natural wetland emissions of methylated trace elements

“…Demethylation reactions by strict anaerobes (for example, Methanococcus) are improbable, on the one hand due to the (sub-)oxic conditions ( À 51 to þ 118 mV) at the wetland surface, and on the other hand because of the low aqueous Se concentrations (nM) 41,42 . More plausible are abiotic oxidation and demethylation reactions (for example, atmospheric instability and photo-oxidation in the transparent flow-through box), but comparing the reactions for Se, S and As is impeded by a lack of mechanistic and kinetic information, and further investigation is required.…”