AUTHOR=Durante-Rodríguez Gonzalo , Fernández-Llamosas Helga , Alonso-Fernandes Elena , Fernández-Muñiz María Nieves , Muñoz-Olivas Riansares , Díaz Eduardo , Carmona Manuel 

TITLE=ArxA From Azoarcus sp. CIB, an Anaerobic Arsenite Oxidase From an Obligate Heterotrophic and Mesophilic Bacterium

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01699

DOI=10.3389/fmicb.2019.01699

ISSN=1664-302X

ABSTRACT=<p>Arsenic is a toxic element widely distributed in nature, but numerous bacteria are able to resist its toxicity mainly through the <italic>ars</italic> genes encoding an arsenate reductase and an arsenite efflux pump. Some “arsenotrophic” bacteria are also able to use arsenite as energy supplier during autotrophic growth by coupling anaerobic arsenite oxidation <italic>via</italic> the <italic>arx</italic> gene products to nitrate respiration or photosynthesis. Here, we have demonstrated that <italic>Azoarcus</italic> sp. CIB, a facultative anaerobic β-proteobacterium, is able to resist arsenic oxyanions both under aerobic and anaerobic conditions. Genome mining, gene expression, and mutagenesis studies revealed the presence of a genomic island that harbors the <italic>ars</italic> and <italic>arx</italic> clusters involved in arsenic resistance in strain CIB. Orthologous <italic>ars</italic> clusters are widely distributed in the genomes of sequenced <italic>Azoarcus</italic> strains. Interestingly, genetic and metabolic approaches showed that the <italic>arx</italic> cluster of the CIB strain encodes an anaerobic arsenite oxidase also involved in the use of arsenite as energy source. Hence, <italic>Azoarcus</italic> sp. CIB represents the prototype of an obligate heterotrophic bacterium able to use arsenite as an extra-energy source for anaerobic cell growth. The arsenic island of strain CIB supports the notion that metabolic and energetic skills can be gained by genetic mobile elements.</p>