Biotransformation and Volatilization of Arsenic by Three Photosynthetic Cyanobacteria1
Biotransformation and Volatilization of Arsenic by Three Photosynthetic Cyanobacteria1
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DOI：
10.1104/pp.111.178947
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发表时间：
2011-05
期刊：
影响因子：
7.4
通讯作者：
Xi Yin;Jian Chen;J. Qin;Guoxin Sun;B. Rosen;Yong-guan Zhu
中科院分区：
文献类型：
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作者：
Xi Yin;Jian Chen;J. Qin;Guoxin Sun;B. Rosen;Yong-guan Zhu
砷（As）是一种普遍存在的环境毒素，已在世界范围内引起人类健康问题.然而，关于生物体如何解毒As的研究很少。蓝细菌能够在光照下异养生长，在黑暗中异养生长，并且在土壤、水生系统和湿地中普遍存在。在这项研究中，我们调查了As的生物转化三种蓝藻（微囊藻属PCC 7806，念珠藻属PCC 7120，集胞藻属PCC 6803）。100 μm亚砷酸钠处理14 d后，三种砷的积累量分别达到0.39 g kg−1、0.45 g kg−1和0.38 g kg−1。无机砷酸盐和亚砷酸盐是主要的物种，砷酸盐占总砷的80%以上，甲基化砷检测后，暴露于较高的砷浓度。当砷处理6周时，每个蓝藻细胞产生挥发性砷。从这三种蓝藻中克隆了编码As（III）S-腺苷甲硫氨酸甲基转移酶（ArsM）的基因。当在大肠杆菌的As-超敏感菌株中表达时，每个都赋予了对亚砷酸盐的抗性。两个ArsM同源物（SsArsM从集胞藻属PCC 6803和NsArsM从念珠藻属PCC 7120）进行了纯化，并显示在体外甲基化亚砷酸三甲基胂作为最终产物。鉴于ArsM同系物广泛存在于蓝藻中，我们建议，他们发挥了重要的作用，在作为地球化学。
Arsenic (As) is a pervasive and ubiquitous environmental toxin that has created worldwide human health problems. However, there are few studies about how organisms detoxify As. Cyanobacteria are capable of both photolithotrophic growth in the light and heterotrophic growth in the dark and are ubiquitous in soils, aquatic systems, and wetlands. In this study, we investigated As biotransformation in three cyanobacterial species (Microcystis sp. PCC7806, Nostoc sp. PCC7120, and Synechocystis sp. PCC6803). Each accumulated large amounts of As, up to 0.39 g kg−1 dry weight, 0.45 g kg−1 dry weight, and 0.38 g kg−1 dry weight when treated with 100 μm sodium arsenite for 14 d, respectively. Inorganic arsenate and arsenite were the predominant species, with arsenate making up >80% of total As; methylated arsenicals were detected following exposure to higher As concentrations. When treated with arsenate for 6 weeks, cells of each cyanobacterium produced volatile arsenicals. The genes encoding the As(III) S-adenosylmethionine methyltransferase (ArsM) were cloned from these three cyanobacteria. When expressed in an As-hypersensitive strain of Escherichia coli, each conferred resistance to arsenite. Two of the ArsM homologs (SsArsM from Synechocystis sp. PCC6803 and NsArsM from Nostoc sp. PCC7120) were purified and were shown to methylate arsenite in vitro with trimethylarsine as the end product. Given that ArsM homologs are widespread in cyanobacteria, we propose that they play an important role in As biogeochemistry.