稻田环境青萍及其叶面微生物砷积累和转化研究

Arsenic contamination in paddy soil environments is a serious threaten to human health and the sustainable agriculture. Arsenic speciation is dominantly a microbe-mediated process, which directly influences arsenic uptake and accumulation by plants. The floating plants, such as duckweeds (Lemnaceae), and the associated phyllosphere microbial communities are important components of the paddy soil environments. Previous studies based on incubational experiments under greenhouse conditions found that the duckweed and the phyllosphere bacterial community drive a dynamic cascade of arsenic species turnover in the surface water. However, in natural paddy soil fields, little information is available while is worthy to find out in terms of arsenic speciation by the phyllosphere microbial community, the effect of these microbe-mediated processes on arsenic accumulation by the duckweed, and among which the key modulating environmental factors. In this proposal, we plan to use Lemna (a duckweed commonly found in paddy soil environments) in a paddy soil field located in Chenzhou, which has been designed for the studies of arsenic biogeochemistry due to the arsenic contamination by mining. By collecting water and Lemna samples according to different rice growing periods, and with the combination of chemical analysis and microbial ecological technologies, such as metagenomic analysis, quantitative PCR and clone library construction, this proposal aims 1) to study the arsenic speciation by the Lemna phyllosphere microbial community; 2) to find the effect of the microbe-mediated arsenic speciation in the phyllosphere on the arsenic accumulation by Lemna. Based on these studies, we intend to reveal the key microbial processes, microbial populations, and environmental factors associated in arsenic biogeochemistry in the surface water of paddy soil fields.

稻田环境中的砷污染严重危害人类健康和农业可持续发展。微生物对砷的形态转化直接影响植物对砷的吸收和累积。稻田表层水体中的浮水植物及其叶面微生物是稻田生态环境的重要组成部分。室内培养研究发现，具有高砷累积能力的浮萍及其叶面微生物在稻田表层水环境中驱动着一个完整的砷氧化还原代谢链。然而在自然条件下的稻田生态系统中，浮萍叶面微生物对砷的转化能力、叶面微生物对浮萍累积砷的作用、以及影响砷吸收和转化的关键环境因子则需要进一步验证。本申请以郴州矿区砷污染稻田中的青萍为研究对象，通过在不同水稻生长季采集样品，采用化学分析与宏基因组测序、荧光定量PCR、克隆文库构建等分子生态学技术相结合的方法，研究在不同的施肥管理下叶面微生物对砷的转化以及对青萍累积砷的影响，寻找稻田表层水环境中砷生物地球化学循环的关键微生物群落及调控因子，为稻田生态系统的可持续开发利用及水环境砷污染修复提供微生物资源和理论基础。