New clusters of arsenite oxidase and unusual bacterial groups in enrichments from arsenic-contaminated soil

Abstract

In the present study cultivation-dependent and molecular methods were applied in combination to investigate the arsenite-oxidizing communities in enrichment cultures from arsenic and lead smelter-impacted soils with respect to both 16S rRNA and arsenite oxidase gene diversity. Enrichments with arsenite as the only electron donor resulted in completely different communities than enrichments with yeast extract and the simultaneous presence of arsenite. The lithoautotrophic community appeared to be dominated by Ferrimicrobium-related Actinobacteria, unusual Acidobacteria, Myxobacteria, and α-Proteobacteria but the heterotrophic community comprised many Dokdonella-related γ-Proteobacteria. Gene sequences of clones encoding arsenite oxidase from the enrichment for lithoautotrophs belonged to three major clusters with sequences from non-cultivated microorganisms. So, primers used to detect arsenite oxidase genes could amplify the genes from many α-, β- and γ-Proteobacteria, but not from various strains of the other phyla present in the enrichment for lithotrophs. This was also observed for the isolates where arsenite oxidase genes from new proteobacterial isolates of the genera Burkholderia, Bosea, Alcaligenes, Bradyrhizobium and Methylobacterium could be amplified but the genes of the new Rhodococcus isolate S43 could not. The results indicate that the ability to oxidize arsenite is widespread in various unusual taxa, and molecular methods for their detection require further improvement.

Microbial community composition of a household sand filter used for arsenic, iron, and manganese removal from groundwater in Vietnam

“…Homologs of genes encoding a respiratory arsenite oxidase (aioA) have been found in phylogenetically diverse microbial taxa including members of Alpha-, Beta-, Gammaproteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, Aquificae, Deinococcus-Thermus, Chlorobi, Chloroflexi, Nitrospira, and Crenarchaeota (Yamamura and Amachi, 2014). aioA-like genes have been amplified from a variety of As-rich environments (Inskeep et al, 2007;Hamamura et al, 2009;Quemeneur et al, 2010;Sultana et al, 2012;Price et al, 2013), but they also been detected in soil or sediments containing background levels of As (Lami et al, 2013;Yamamura et al, 2013). OTUs belonging to Proteobacteria, Nitrospira, and Crenarchaeota comprising potential arsenite respirers were also present in the pyrosequencing libraries of the sand filter samples.…”

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

“…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]). The supposition that a so-far-unknown protein takes part in the arsenite oxidation in this strain is in concert with the fact that arsenite oxidases are an ancient (64,65) and very diverse group of proteins (66) far from being fully explored (67). Although the enzymes involved are not yet identified in Synechocystis, it is noteworthy that arsenite oxidation to arsenate via electron transport to plastoquinone is energetically more favorable than the reverse reaction according to the more negative midpoint redox potential of arsenate/arsenite (ϩ60 mV) (20) compared to that of plastoquinones (ϩ80 mV) (68).…”

Arsenite as an Electron Donor for Anoxygenic Photosynthesis: Description of Three Strains of Ectothiorhodospira from Mono Lake, California and Big Soda Lake, Nevada

“…The arsenite oxidase gene, aioA was detected using primers reported in Sultana, et al [26]: AOX-F-A2: 5’-TGCATCGTCGGCTGYGGNTAY-3’ and AOX-R-E2: 5’-TTCGGAGTTATAGGCCGGNCKRTTRTG-3’. The arxA PCR conditions were: 200 nM of each primer, 2× Taq mixture from Promega, and template DNA (~10–50 ng).…”