The diversity of membrane transporters encoded in bacterial arsenic-resistance operons.

Yiren Yang,Shiyang Wu,Ren Zhang,Ross Mccausland Lilley

doi:10.7717/peerj.943

Abstract

Transporter-facilitated arsenite extrusion is the major pathway of arsenic resistance within bacteria. So far only two types of membrane-bound transporter proteins, ArsB and ArsY (ACR3), have been well studied, although the arsenic transporters in bacteria display considerable diversity. Utilizing accumulated genome sequence data, we searched arsenic resistance (ars) operons in about 2,500 bacterial strains and located over 700 membrane-bound transporters which are encoded in these operons. Sequence analysis revealed at least five distinct transporter families, with ArsY being the most dominant, followed by ArsB, ArsP (a recently reported permease family), Major Facilitator protein Superfamily (MFS) and Major Intrinsic Protein (MIP). In addition, other types of transporters encoded in the ars operons were found, but in much lower frequencies. The diversity and evolutionary relationships of these transporters with regard to arsenic resistance will be discussed.

Highlights

Arsenic (As) is the 53rd most abundant element in the earth’s crust, but is the most ubiquitous environmental toxin and carcinogen (Zhu et al, 2014)
Classification of membrane transporters encoded in ars operons Of about 2500 bacterial genomes surveyed, 685 ars operons were identified and 717 putative membrane transporters were extracted
A number of experimentally characterized arsenic transporters were included in our study, including ArsB (Chen et al, 1986; Broer et al, 1993; Bruhn et al, 1996; Ryan & Colleran, 2002), ArsY (ACR3) (Hu et al, 2011; Bhat et al, 2011), Aqps (Yang et al, 2005) and GlpF (Meng, Liu & Rosen, 2004)

Summary

INTRODUCTION

Arsenic (As) is the 53rd most abundant element in the earth’s crust, but is the most ubiquitous environmental toxin and carcinogen (Zhu et al, 2014). Since ArsY is homologous to the yeast arsenic transporter ACR3 (Bobrowicz et al, 1997), this group of arsenite transporters have been assigned into the ACR3 (or Acr3) family (Rosen, 1999). Two other putative transporters belonging to the major facilitator superfamily (MFS) have been identified as the assumed products of bacterial ars operons (Chauhan et al, 2009; Drewniak et al, 2013). These indicate that, in addition to ArsB and ArsY, other membrane transporters have been recruited to deal with arsenic toxins in some bacteria. Our findings indicate that bacteria employ more diverse membrane transporters than previously known in combating arsenic toxicity

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSIONS