Bioadsorption and microbe-mediated reduction of Sb(V) by a marine bacterium in the presence of sulfite/thiosulfate and the mechanism study

Microbe-Sb interactions remain poorly understood and the molecular mechanism of microbe-mediated Sb(V) reduction remains unclear. In the present study, we investigated the process and mechanism of Sb(V) bioreduction by Shewanella sp. CNZ-1, which was isolated from the sediment of the Bohai Strait, in the absence or presence of sulfate/sulfite/thiosulfate. Results demonstrate that Sb(V) could be reduced to Sb(III) (including Sb2O3 and Sb(III)(aq) etc.) by CNZ-1 cells. Kinetic studies are carried out using the Langmuir-Freundlich dual model and Monod model and the results reveal that Sb removal by strain CNZ-1 is a fast bioadsorption (KLF, 1/n and a are 8.03, 0.0032 and 0.95, respectively; R-2= 0.98) and slow bioreduction (R-2= 0.95) process. Moreover, the supplementation of SO32- and S2O32- into the reaction system can lead to the formation of Sb2S3 along with the reduction of SO32- and S2O32-, while SO42- can't. The precipitates of Sb2S3 and Sb2O3 are further characterized and confirmed by SEM-EDX, XPS and XRD. In addition, global transcriptome assays reveal that genes encoding dehydrogenase, cytochrome, reductase, stress resistance protein, membrane proteins and transporters play key roles during the transformation of SO32-/S2O32- by CNZ-1 cells and subsequent RT-qPCR assays show that the genes S. CNZ. 1GM004058 and S. CNZ. 1GM001069 should account for the reduction of SO32- and S2O32- by the CNZ-1 strain, respectively.