Xue Xi-Mei, Yan Yu, Xiong Chan, Raber Georg, Francesconi Kevin, Pan Ting, Ye Jun, Zhu Yong-Guan
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Environ Pollut. 2017 Sep;228:111-117. doi: 10.1016/j.envpol.2017.05.005. Epub 2017 May 18.
Nostoc sp. PCC 7120 (Nostoc), a typical filamentous cyanobacterium ubiquitous in aquatic system, is recognized as a model organism to study prokaryotic cell differentiation and nitrogen fixation. In this study, Nostoc cells incubated with arsenite (As(III)) for two weeks were extracted with dichloromethane/methanol (DCM/MeOH) and the extract was partitioned between water and DCM. Arsenic species in aqueous and DCM layers were determined using high performance liquid chromatography - inductively coupled plasma mass spectrometer/electrospray tandem mass spectrometry (HPLC-ICPMS/ESIMSMS). In addition to inorganic arsenic (iAs), the aqueous layer also contained monomethylarsonate (MAs(V)), dimethylarsinate (DMAs(V)), and the two arsenosugars, namely a glycerol arsenosugar (Oxo-Gly) and a phosphate arsenosugar (Oxo-PO4). Two major arsenosugar phospholipids (AsSugPL982 and AsSugPL984) were detected in DCM fraction. Arsenic in the growth medium was also investigated by HPLC/ICPMS and shown to be present mainly as the inorganic forms As(III) and As(V) accounting for 29%-38% and 29%-57% of the total arsenic respectively. The total arsenic of methylated arsenic, arsenosugars, and arsenosugar phospholipids in Nostoc cells with increasing As(III) exposure were not markedly different, indicating that the transformation to organoarsenic in Nostoc was not dependent on As(III) concentration in the medium. Our results provide new insights into the role of cyanobacteria in the biogeochemical cycling of arsenic.
集胞藻PCC 7120（蓝藻）是水生系统中普遍存在的一种典型丝状蓝细菌，被公认为是研究原核细胞分化和固氮作用的模式生物。在本研究中，用二氯甲烷/甲醇（DCM/MeOH）提取了与亚砷酸盐（As(III)）孵育两周的蓝藻细胞，提取物在水和DCM之间进行分配。使用高效液相色谱 - 电感耦合等离子体质谱仪/电喷雾串联质谱仪（HPLC-ICPMS/ESIMSMS）测定水层和DCM层中的砷形态。除了无机砷（iAs）外，水层还含有一甲基砷酸（MAs(V)）、二甲基砷酸（DMAs(V)）以及两种砷糖，即甘油砷糖（Oxo-Gly）和磷酸砷糖（Oxo-PO4）。在DCM组分中检测到两种主要的砷糖磷脂（AsSugPL982和AsSugPL984）。还通过HPLC/ICPMS对生长培养基中的砷进行了研究，结果表明其主要以无机形态As(III)和As(V)存在，分别占总砷的29%-38%和29%-57%。随着As(III)暴露量增加，蓝藻细胞中甲基化砷、砷糖和砷糖磷脂的总砷含量并无显著差异，这表明蓝藻中向有机砷的转化不依赖于培养基中As(III)的浓度。我们的研究结果为蓝细菌在砷的生物地球化学循环中的作用提供了新的见解。
