ArxA, a new clade of arsenite oxidase within the DMSO reductase family of molybdenum oxidoreductases

Abstract

Arsenotrophy, growth coupled to autotrophic arsenite oxidation or arsenate respiratory reduction, occurs only in the prokaryotic domain of life. The enzymes responsible for arsenotrophy belong to distinct clades within the DMSO reductase family of molybdenum-containing oxidoreductases: specifically arsenate respiratory reductase, ArrA, and arsenite oxidase, AioA (formerly referred to as AroA and AoxB). A new arsenite oxidase clade, ArxA, represented by the haloalkaliphilic bacterium Alkalilimnicola ehrlichii strain MLHE-1 was also identified in the photosynthetic purple sulfur bacterium Ectothiorhodospira sp. strain PHS-1. A draft genome sequence of PHS-1 was completed and an arx operon similar to MLHE-1 was identified. Gene expression studies showed that arxA was strongly induced with arsenite. Microbial ecology investigation led to the identification of additional arxA-like sequences in Mono Lake and Hot Creek sediments, both arsenic-rich environments in California. Phylogenetic analyses placed these sequences as distinct members of the ArxA clade of arsenite oxidases. ArxA-like sequences were also identified in metagenome sequences of several alkaline microbial mat environments of Yellowstone National Park hot springs. These results suggest that ArxA-type arsenite oxidases appear to be widely distributed in the environment presenting an opportunity for further investigations of the contribution of Arx-dependent arsenotrophy to the arsenic biogeochemical cycle.

Coregulated Genes Link Sulfide:Quinone Oxidoreductase and Arsenic Metabolism in Synechocystis sp. Strain PCC6803

“…Although this phenomenon has been characterized in purple sulfur bacteria (63), experimental observations of the green mats from the hot spring pond at Mono Lake suggested that the Oscillatoria-type cyanobacteria that dominated the green mat may also be capable of As(III)-supported anoxygenic photosynthesis (21). In the genome of Synechocystis, no homologs of known arsenite oxidases can be found either (according to its annotation as well as BLAST searches using bacterial AoxA, AoxB, ArrA, and ArxA sequences as query [data not shown]).…”

Metagenomic study of red biofilms from Diamante Lake reveals ancient arsenic bioenergetics in haloarchaea

“…A phylogenetic analysis of all the haloarchaea AioA and ArrA within the CISM family showed not only that they clustered together with all known AioA and ArrA proteins, respectively, but also that both form a robust monophyletic branch within the group of each enzyme (Supplementary Figure 2). It worth noting that the haloarchaea ArrA proteins are clearly clustering together with all the other known ArrA enzymes and are not related to the recently described ArxA proteins (a clade of arsenite oxidases, proposed to be ancestor of the ArrA, which catalyze the oxidative reverse reaction; Zargar et al, 2012).…”

Microbial Antimony Biogeochemistry: Enzymes, Regulation, and Related Metabolic Pathways

“…Bacterial As(III) oxidation involves the As(III) oxidase AioBA or ArxAB (120,121). AioBA functions as an aerobic As(III) oxidase (122), while ArxAB catalyzes the anaerobic oxidation of As(III) (121).…”