Anaerobic Respiration On Nitarsone In Aquatic Environments By Shewanella Oneidensis Mr-1 Lacking Known C Center Dot As Lyases

Nitarsone, the extensively used organoarsenical in poultry production has resulted in the elevated level of arsenic in aquatic environments, further influencing the arsenic cycling and increasing the carcinogenic risk. The electron-withdrawing property of nitro-group makes nitarsone high resistance to direct oxidative degradation, while anaerobic degradation by microbes is an ideal candidate. However, so far, no microbial degradation of nitarsone under anaerobic conditions has been reported yet. In this work, Shewanella oneidensis MR-1, a model and widespread strain in aquatic environments, is demonstrated to be able to anaerobically respire on nitarsone. The extracellular electron transfer pathways play essential roles in anaerobic nitarsone reduction. Modularity exists among MtrA, MtrB, and MtrC paralogues in the anaerobic nitarsone reduction by S. oneidensis MR-1. Dosing anthraquinone-2,6-disulfonate as a mediator considerably raises the nitarsone reduction rate. Reduction products analysis and density functional theory (DFT) calculations suggest that reducing equivalents first go to the nitro group of nitarsone, followed by the cleavage reaction of C.As bond of reduction products by a novel C center dot As lyase. This work sheds new lights on the roles of dissimilatory metal-reducing bacteria like Shewanella in nitarsone biotransformation, elucidates the mechanism behind such a biotransformation process at molecular level and provides useful information about bioremediation of nitarsone-contaminated aquatic environments.