Arsenic transport system by plant-soil microorganism interaction

我们从水稻根际分离出两种负责As甲基化的细菌。菌株GSRB54和GSRB05通过16S rRNA测序分别归属于链霉菌属和伯克霍尔德菌属。GSRB54的亚砷酸盐s -腺苷蛋氨酸甲基转移酶（arsM）基因在系统发育上与其他已知细菌的arsM基因不同。在大肠杆菌中异源表达GSRB54 arsM可将As（III）甲基化转化为DMA。另一方面，菌株GSRB05产生未知有机砷化合物（uAs1）。通过LC/MS/MS、1H、13C-NMR和2D-NMR分析，证实其化学结构为单甲基化As部分结构的氨基酸衍生物，命名为Arsenothricin （AST）。这些结果表明，本研究分离的细菌通过水稻根际As甲基化与水稻籽粒中甲基化As积累有关。

We isolated from the rice rhizosphere two bacteria responsible for As methylation. Strain GSRB54 and GSRB05 were classified into the genus Streptomyces and Burkholderia, respectively, by 16S rRNA sequencing. The arsenite S-adenosylmethionine methyltransferase (arsM) gene of GSRB54 was phylogenetically different from known arsM genes in other bacteria. Heterologous expression of GSRB54 arsM in E. coli converted the methylation of As(III) into DMA. On the other hand, strain GSRB05 produced an unknown organic As compound (uAs1). The analyses by using LC/MS/MS, 1H, 13C-NMR and 2D-NMR elucidated that the chemical structure of uAs1 is amino acid derivative with a monomethylated As partial structure and we named it as Arsenothricin (AST). AST was degraded into MMA by Arthrobacter sp. These results suggest that the bacteria isolated from this study are associated with methylated As accumulation in rice grains through As methylation in the rice rhizosphere.