State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark.
Environ Microbiol. 2015 Jun;17(6):1926-40. doi: 10.1111/1462-2920.12465. Epub 2014 Apr 28.
The fate of arsenate (As(V) ) generated by microbial arsenite (As(III) ) oxidation is poorly understood. Agrobacterium tumefaciens wild-type strain (GW4) was studied to determine how the cell copes with As(V) generated in batch culture. GW4 grown heterotrophically with mannitol used As(III) as a supplemental energy supply as reflected by enhanced growth and increased cellular levels of NADH and ATP. Under low phosphate (Pi) conditions and presence of As(III) oxidation, up to ∼ 50% of the resulting As(V) was taken up and found associated with the periplasm, membrane or cytoplasm fractions of the cells. Arsenic was found associated with proteins and polar lipids, but not in nucleic acids or sugars. Thin-layer chromatography and gas chromatography-mass spectrometry analysis suggested the presence of arsenolipids in membranes, presumably as part of the bilayer structure of the cell membrane and replacing Pi under Pi-limiting conditions. The potential role of a Pi-binding protein (PstS) for As(V) uptake was assessed with the His-tag purified protein. Intrinsic tryptophan fluorescence spectra analysis suggests that PstS can bind As(V) , but with lower affinity as compared with Pi. In early stationary phase cells, the As(V) : Pi ratio was approximately 4.3 and accompanied by an altered cell ultrastructure.
砷酸盐（As(V)）的命运是由微生物亚砷酸盐（As(III)）氧化产生的，但目前对此知之甚少。本研究以根癌农杆菌野生型菌株（GW4）为研究对象，以确定细胞如何应对分批培养中产生的 As(V)。GW4 异养生长并利用甘露醇作为补充能源供应，这反映在增强的生长和增加的 NADH 和 ATP 细胞水平上。在低磷酸盐（Pi）条件和存在 As(III)氧化的情况下，多达约 50%的生成的 As(V)被吸收，并发现与细胞的周质、膜或细胞质部分相关。砷与蛋白质和极性脂质有关，但与核酸或糖无关。薄层层析和气相色谱-质谱分析表明，膜中存在砷脂，可能作为细胞膜双层结构的一部分，并在 Pi 限制条件下替代 Pi。用 His 标记纯化蛋白评估了 Pi 结合蛋白（PstS）对 As(V)摄取的潜在作用。本研究通过固有色氨酸荧光光谱分析表明，PstS 可以结合 As(V)，但亲和力低于 Pi。在早期稳定期细胞中，As(V) ：Pi 的比例约为 4.3，并伴有细胞超微结构的改变。
