全球稻田面积约1.5亿公顷，75%处于淹水状态。厌氧环境使得水稻土含有丰富的小分子有机酸。通过代谢这些物质，微生物驱动着稻田土壤生物地球化学循环过程。甲酸是稻田有机质降解过程中重要中间产物之一，但水稻土中甲酸代谢微生物及其生态功能却鲜有报道。
中科院南京土壤研究所林先贵研究员团队通过稳定性同位素核酸探针技术，利用13C标记的甲酸培育水稻土，让微生物“吃掉”甲酸的13C；再利用超高速密度梯度离心对土壤总DNA进行分层，获得甲酸代谢微生物13C-DNA；借助实时定量PCR技术、指纹图谱技术和系统发育分析，清楚表明13C-甲酸被土壤梭菌和紫色非硫细菌利用。前者可利用甲酸为电子供体促进水稻土中硫酸盐和铁还原过程；紫色非硫细菌是首次原位条件下被发现可在黑暗中有机异养生长。
这些结果不仅仅揭示了水稻土中甲酸代谢微生物，更扩展了人们对甲酸在生物地球化学循环过程中重要性的认知，为全面理解微生物驱动下的土壤养分循环过程及其调控机制提供了重要科学依据。
该成果发表在Soil Science Society of America Journal上，并选为研究亮点在美国农作物科学协会(Crop Science Society of America)创办的CSA (Crops， Soils， Agronomy) news 杂志的2012年2月刊上报道。（生物谷Bioon.com）
doi:10.2136/sssaj2011.0216
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Identification of Formate-Metabolizing Bacteria in Paddy Soil by DNA-Based Stable Isotope Probing
Youzhi Feng, Xiangui Lin *, Zhongjun Jia and Jianguo Zhu
As one of the fermentation products of plant biomass, formate is an important organic acid in flooded rice (Oryza sativa L.) fields. Little is known, however, about the identity of formate-metabolizing bacteria in paddy soil. In this study, a paddy soil microcosm was incubated with 13C-labeled formate; bacterial and eukaryotic communities incorporating formate C were analyzed by DNA-stable isotope probing. Real-time quantitative polymerase chain reaction analysis revealed that 13C-formate-derived C was actively assimilated by a subset of bacteria. Molecular fingerprinting and sequencing analysis of 16S rRNA genes revealed that the active formate-metabolizing bacteria in the paddy soil were mainly the bacteria in the Clostridia class and purple nonsulfur bacteria (PNSB). The former might facilitate SO42− and Fe reduction using formate. Observed for the first time, PNSB are able to assimilate organic matter for growth under in situ conditions without light. These results extend our knowledge of not only the formate-assimilating bacteria but also the ecological significance of formate in paddy soil.
