Distribution of Arsenic Resistance Genes in Prokaryotes.

Ibtissem Ben Fekih,Yi Zhao,Christopher Rensing,Hend A Alwathnani,Carlos Cervantes,Chengkang Zhang,Quaiser Saquib,Yuan Ping Li

doi:10.3389/fmicb.2018.02473

Abstract

Arsenic is a metalloid that occurs naturally in aquatic and terrestrial environments. The high toxicity of arsenic derivatives converts this element in a serious problem of public health worldwide. There is a global arsenic geocycle in which microbes play a relevant role. Ancient exposure to arsenic derivatives, both inorganic and organic, has represented a selective pressure for microbes to evolve or acquire diverse arsenic resistance genetic systems. In addition, arsenic compounds appear to have been used as a toxin in chemical warfare for a long time selecting for an extended range of arsenic resistance determinants. Arsenic resistance strategies rely mainly on membrane transport pathways that extrude the toxic compounds from the cell cytoplasm. The ars operons, first discovered in bacterial R-factors almost 50 years ago, are the most common microbial arsenic resistance systems. Numerous ars operons, with a variety of genes and different combinations of them, populate the prokaryotic genomes, including their accessory plasmids, transposons, and genomic islands. Besides these canonical, widespread ars gene clusters, which confer resistance to the inorganic forms of arsenic, additional genes have been discovered recently, which broadens the spectrum of arsenic tolerance by detoxifying organic arsenic derivatives often used as toxins. This review summarizes the presence, distribution, organization, and redundance of arsenic resistance genes in prokaryotes.

Highlights

Arsenic is a metalloid that occurs naturally in aquatic and terrestrial environments
The legume symbiont Sinorhizobium meliloti possesses a distinct ars operon encoding the aquaglyceroporin AqpS, which may function as an arsenite efflux pump that substitutes for the ArsB transporter (Figure 1)
Acr3 and ArsP transporters coexist in the C. jejuni ars operon (Figure 1), where they participate in the extrusion of inorganic and organic arsenicals, respectively (Shen et al, 2014)

Summary

Introduction

Arsenic is a metalloid that occurs naturally in aquatic and terrestrial environments. ArsD functions as an inducer-independent, weak repressor of the ars operon, but its primary role is related to its ability to bind arsenite and transfer it to the ArsA ATPase prior to the oxyanion extrusion by the ArsB pump (Lin et al, 2006; reviewed in Yang et al, 2012). That the Bacillus arsenite efflux pump is a novel transporter with homology to Acr3, a protein encoded by the yeast Saccharomyces cerevisiae, which confers arsenic resistance (Ghosh et al, 1999).

Results

Conclusion