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Arsenate Resistance in the Unicellular Marine Diazotroph Crocosphaera watsonii

机译:单细胞海洋重氮菌克氏菌对砷的抗药性

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摘要

The toxic arsenate ion can behave as a phosphate analog, and this can result in arsenate toxicity especially in areas with elevated arsenate to phosphate ratios like the surface waters of the ocean gyres. In these systems, cellular arsenate resistance strategies would allow phytoplankton to ameliorate the effects of arsenate transport into the cell. Despite the potential coupling between arsenate and phosphate cycling in oligotrophic marine waters, relatively little is known about arsenate resistance in the nitrogen-fixing marine cyanobacteria that are key components of the microbial community in low nutrient systems. The unicellular diazotroph, Crocosphaera watsonii WH8501, was able to grow at reduced rates with arsenate additions up to 30 nM, and estimated arsenate to phosphate ratios of 6:1. The genome of strain WH8501 contains homologs for arsA, arsH, arsB, and arsC, allowing for the reduction of arsenate to arsenite and the pumping of arsenite out of the cell. The short-term addition of arsenate to the growth medium had no effect on nitrogen fixation. However, arsenate addition did result in the up-regulation of the arsB gene with increasing arsenate concentrations, indicating the induction of the arsenate detoxification response. The arsB gene was also up-regulated by phosphorus stress in concert with a gene encoding the high-affinity phosphate binding protein pstS. Both genes were down-regulated when phosphate was re-fed to phosphorus-stressed cells. A field survey of surface water from the low phosphate western North Atlantic detected expression of C. watsonii arsB, suggestive of the potential importance of arsenate resistance strategies in this and perhaps other systems.
机译:有毒的砷酸根离子可充当磷酸根类似物,这会导致砷酸根中毒,尤其是在砷酸根与磷酸根之比升高的区域(例如大洋回转的地表水)中。在这些系统中,细胞对砷酸盐的抗性策略将使浮游植物改善砷酸盐向细胞内转运的影响。尽管在贫营养海水中砷酸盐和磷酸盐循环之间存在潜在的耦合,但对于固氮海洋蓝细菌中低砷系统中微生物群落的关键组成部分-砷的抗药性知之甚少。单细胞重氮营养菌华豆鳄属WH8501能够以降低的速率生长,砷的添加量高达30 nM,砷和磷酸盐的比例估计为6:1。菌株WH8501的基因组包含arsA,arsH,arsB和arsC的同源物,可将砷酸盐还原为亚砷酸盐,并从细胞中抽出砷。短期向生长培养基中添加砷酸盐对固氮没有影响。但是,添加砷酸盐确实会导致arsB基因随着砷酸盐浓度的增加而上调,表明诱导了砷酸盐解毒反应。磷胁迫还与编码高亲和力磷酸盐结合蛋白pstS的基因协同上调了arsB基因。当将磷酸盐重新喂给磷胁迫的细胞时,这两个基因均被下调。来自北大西洋西部低磷酸盐地区的地表水的现场调查检测到了沃森梭菌arsB的表达,这表明在此系统以及其他系统中,砷酸抗性策略的潜在重要性。

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