Bioremediation of heavy metals by an unexplored bacterium, Pseudoxanthomonas mexicana strain GTZY, isolated from aerobic-biofilm wastewater system

Abstract We prompted first to characterize a wastewater bacterium, Pseudoxanthomonas mexicana GTZY, that efficiently transforms toxic mercury and arsenic and to explore its bioremediation capability and to reveal their relevant gene resistance operons. The Isolated strain was characterized for its phylogenetic, biochemical and phenotypic properties. The strain GTZY potentially removed 84.3% of mercury and their mercury volatilization (Hg(II) to Hg(0)) was confirmed using X-ray film method, and its respective merA gene was PCR amplified. In addition, strain GTZY was efficiently removed arsenate (68.5%) and arsenite (63.2%), and showed resistance up to >175 and >55 mM, respectively. Their genomic annotations were disclosed the linkage of Tn2-transposon and int1 in both ends of meroperon (merAPTR). The co-existence of arsP and arsH proteins in its intrinsic ars operon (arsCPRH) was extremely diverse from its ancestral species. We believe that mercury resistance-conferring meroperon of P. mexicana GTZY presumably derived horizontally from other species in the reactor, while arsenic resistance-conferring intrinsic ars operon was highly diversified and evolved from its ancestral species. By considering the potential of the strain GTZY to transform heavy metals, this can be used to recover contaminated sites.