3As, such proteins were less abundant in the presence of As(III). In addition to these proteins, it was observed that enzymes involved in major carbon metabolism (glycolysis, neoglucogenesis) or energy metabolism (thiosulfate oxidation, oxidative MG-132 phosphorylation) were less abundant in 3As in the presence of As(III). This observation correlated with the phenotypic observation that the strain 3As grew better in the absence of arsenic (Table 1). Discussion Two groups could be distinguished within the Thiomonas strains studied: Group I comprises all the strains in this study except T. arsenivorans, which is part of a second group, Group II. As described by Moreira and Amils [17], all of the strains grew

better in mixotrophic media containing both thiosulfate and organic supplements, and used RISCs as an energy source. This suggests that lithotrophy is a general characteristic of the Thiomonas genus. In contrast, neither strain Ynys1 nor T. selleck chemicals llc perometabolis could grow organotrophically in the absence of a reduced sulfur compound, suggesting that, despite previous findings, facultative organotrophy is not a general property of the Thiomonas genus. To improve our understanding of these important arsenic-resistant bacteria, several metabolic and genetic properties were investigated.

It appears that much greater physiological differentiation regarding arsenic response was possible between these Thiomonas strains than may have been previously suggested. Clearly Liproxstatin-1 research buy organisms that are phylogenetically close can differ greatly physiologically, in particular concerning specific metabolic traits such as the metabolism of arsenic. For example, Phosphoglycerate kinase the effects

of arsenic on the motility of all strains appeared to be somewhat random, and cannot easily be related to any of the phylogenetic or physiological data obtained. It is worth noting that both T. arsenivorans and WJ68 strains exhibited increased motility in the presence of arsenic. This may indicate a potential energetic role of the element for these strains, as proposed for the arsenic-oxidising bacterium, H. arsenicoxydans [25]. Other physiological divergences concern arsenic resistance. Ynys1 and T. perometabolis were approximately twice as sensitive to As(III) as the other strains. Moreover, the inhibitory effect of arsenite on Ynys1 motility suggests a greater susceptibility of this strain to the metalloid. This could be due to the absence of aox or ars genes. Indeed, these two strains are unable to oxidize As(III), probably as they lack aox genes. Moreover, arsB2 genes were not detected in Ynys1 and T. perometabolis. Therefore, it is probable that these two strains have only a single set of arsenic resistance genes that can be expressed. Interestingly, WJ68 was found to be equally resistant to arsenic as these strains, yet no arsB2 gene could be amplified by PCR. The same is true for T.