Furthermore, strains containing both the arsenite oxidase and any type of transporter gene showed a higher Belinostat cell line arsenite resistance level. These results

suggest that bacteria capable of both arsenite oxidation and arsenite efflux mechanisms have an elevated arsenite resistance level. We also found that arsenite can be fully oxidized even at concentrations close to the MIC in arsenite oxidizers SY8 and TS44 (data not shown). Recently, we have amplified and sequenced the arsC/ACR3 operon (arsC 1-arsR-arsC 2-ACR3-arsH) in the adjacent downstream region of aoxB in Pseudomonas. sp. TS44 (data not shown; GenBank, EU311944). Kashyap et al. [31] found that in Agrobacterium tumefaciens strain 5A, disruption of aoxR caused a loss in the ability to oxidize arsenite and furthermore resulted in an apparent reducing phenotype probably due to the action of cytosolic ArsC and subsequent pumping out of As(III). It is noteworthy to point out that there are two processes of As(V)

reduction in the environment. One is the Semaxanib solubility dmso use of As(V) as a terminal electron acceptor under anaerobic conditions. The other is the intracellular reduction of As(V) to As(III) under aerobic conditions due to the ArsC-dependent cytoplasmic arsenate reduction as part of the arsenic resistance system (ars operon). Since As(III) is the species being pumped out of cell (by arsB or ACR3), the buy Mizoribine presence of Edoxaban As(III) in the environments can also be detected under aerobic condition. One of the main purposes in this research was

to determine the correlation among the bacterial arsenite resistance level, bacterial distribution in the environment and the different types of arsenite transporter gene families. We found that the ACR3 genotypes were predominant over arsB (33 ACR3 vs. 18 arsB) in our samples which was in agreement with a report by Achour et al. [16]. In addition, we found any two types of arsenite transporter genes can coexist in the same strain [arsB and ACR3(1), arsB and ACR3(2), ACR3(1) and ACR3(2)]. Related reports also found the presence of multiple sets of arsenic resistance genes and operons in one strain, especially the arsenite transporter genes. Pseudomonas putida KT2440 contains two operon clusters (arsRBCH) for arsenic resistance [38]. Acidithiobacillus caldus has three sets of arsenic resistance determinants, one located on the chromosome and the other two exist on the transposon [39, 40]. Corynebacterium glutamicum has two typical arsenic-resistant operons and additional arsB and arsC genes, of which two arsenite transporter genes belonged to the ACR3(1) group [41]. The genome of Herminiimonas arsenicoxydans revealed the presence of four arsenic resistance operons including two arsB genes and one ACR3 [42]. Multiple sets of arsenic resistance determinants were also reported in B. subtilis [18] and Desulfovibrio desulfuricans G20 [43].