鞘氨醇杆菌FY-1还原挥发二甲基砷的分子机制研究

五价二甲基砷（DMAs(V)）是土壤中微生物砷甲基化的主要产物，其在水稻中的积累可诱发水稻直穗病，导致减产。土壤中的一些微生物可将DMAs(V)还原挥发为气态的二甲基胂化氢（DMAs(III)H），该过程有可能用于消减环境中DMAs(V)残留。目前关于该过程的研究刚刚起步，机理尚不清楚。在近期的研究中，申请人从一份水稻直穗病发病土壤中分离到一株好氧DMAs(V)挥发菌株Sphingobacterium sp.（鞘氨醇杆菌）FY-1，初步研究表明该菌株具有很强的DMAs(V)挥发能力，外源添加该菌株能促进稻田土壤的DMAs(V)挥发能力。本项目将基于前期的研究积累，采用基因克隆、基因序列与转录分析、酶学研究等手段,鉴定并功能验证菌株FY-1中负责DMAs(V)还原挥发的基因。预期目标是阐明菌株FY-1挥发DMAs(V)的分子机制，为后续利用生物手段消减DMAs(V)残留提供理论支撑。

Dimethylarsenate (DMAs(V)) is a main product of arsenic methylation by soil microorganisms. The accumulation of DMAs(V) in rice can induce straighthead disease, resulting in yield losses. Some soil microbes can reduce DMAs(V) to produce volatile dimethylarsine (DMAs(III)H); this ability may be explored as a potential bioremediation method to eliminate DMAs(V) residue in the soil. However, the research about this biological process is just beginning, and the related mechanisms involved are still unclear. We have recently isolated a pure cultured aerobic DMAs(V)-volatilizing bacterial strain Sphingobacterium sp. FY-1 from a paddy soil in which rice straighthead disease occurred. This strain possesses a strong ability to convert DMAs(V) to produce DMAs(III)H. We found that inoculation of strain FY-1 into the paddy soil enhanced the production of DMAs(III)H. The aim of this proposal is to clone and characterize the functions of the genes responsible for the reduction and volatilization of DMAs(V) in strain FY-1 by using the methods including gene cloning, gene sequence and transcription analysis and enzymological study. The results of the proposed research will elucidate the molecular mechanism of the reductive volatilization of DMAs(V) by strain FY-1 and provide a theoretical basis for bioremediation of the DMAs(V)-contaminated environments.