Sequences with function supported with experimental data marked with asterisk. Scale bar indicates 0.06 amino acid substitutions per site. Branch ends labeled with bootstrap values >50%. Full tree available in the figure in Additional file 1 and all sequences used are listed in the table provided in Additional file 2. The genome neighborhood of Arth_4248 consists of a 10.6-kb region of five putative chromate

resistance genes and three proximal genes of unknown function located on a 96-kb plasmid (Figure 2). Of five genes check details similar to ones associated with Cr(VI) resistance in other organisms, two encode ChrA efflux protein orthologs (Arth_4248 and 4251) and three are similar to different regions of a putative regulatory protein, ChrB (Arth_4249, 4253 and 4254). The remaining three genes (Arth_4247, 4252 and 4255) have not been previously shown to be associated with chromate resistance. The region between Arth_4251 and Arth_4249 is an approximate 1.3 kb region of low complexity. Currently, there is no strong indication of functional genes within this region. Figure 2 Comparison of genetic determinants of chromate resistance as studied in other bacterial strains versus Arthrobacter find more sp. strain FB24. R. sp. RHA1, Rhodococcus sp. RHA1 [GenBank: NC_008268]; N. sp. JS614, Nocardiodes sp. JS614 [GenBank: NC_008699]; A. CHR15, Arthrobacter sp. CHR15 plasmid pCHR15 [6, 35]; C. met. chr1 and chr2, C. metallidurans chromate resistance determinants

1 (plasmid pMOL28) and 2 (chromosomal) [21]; P. aer., Pseudomonas Akt inhibitor aeruginosa plasmid pUM505 [20]; TnOtChr, transposable element from Ochrobactrum tritici 5bv11 [58]; S. ANA-3, Shewanella sp. strain chrBAC operon, plasmid 1 [GenBank: CP000470]. Drawing not to scale. The chromate resistance determinant in Arthrobacter sp. strain FB24 has a similar genetic arrangement to that found in chromate-resistant Arthrobacter sp. CHR15, but is markedly different than in the two well-studied Proteobacteria, P. aeruginosa and C. metallidurans (Figure 2). More recently, a transposable element conferring chromate

resistance in Ochrobactrum tritic was found to have a similar genetic makeup to Orotidine 5′-phosphate decarboxylase the chr1 determinant in C. metallidurans [17], while a chromate resistance operon containing chrA, chrB and chrC was found in Shewanella sp. strain ANA-3 [16]. Additional genes involved in chromate resistance in C. metallidurans, such as the superoxide dismutase gene chrC, chrI and rpoH [21] are not present within the CRD of strain FB24. This could point to functional and regulatory differences in chromate resistance between these distantly related taxa. Thus, we were led to investigate Arth_4247, 4252 and 4255, as well as previously characterized chrA and chrB sequences. Due to the potential involvement of Arth_4247, 4252 and 4255 in chromate resistance, we have named these genes chrL, chrK and chrJ, respectively (Figures 2 and 3). Figure 3 Schematic of constructs used in complementation experiments with strain D11. Panel A: 10.