磷酸盐浓度对微生物铁还原过程的影响

微生物铁还原过程对淹水稻田中水体富营养化调控具有重要的作用，但高浓度磷酸盐对氧化铁的微生物过程是否产生抑制尚不清楚．为此采用土壤泥浆厌氧培养、接种水稻土浸提液混合培养和铁还原菌纯培养等方法，探讨了磷酸盐浓度对微生物铁还原过程的影响程度．结果表明：在水稻土泥浆培养过程中，Fe（Ⅲ）还原速率随磷酸盐浓度增加而降低，淹水后期高浓度磷酸盐处理中的Fe（Ⅱ）累积量呈下降趋势；磷营养为4～16mmol／L时，四川水稻土中的微生物群落能较好地利用葡萄糖和丙酮酸盐进行Fe（OH）3还原反应，江西水稻土中的铁还原微生物群落对葡萄糖的响应时间有所延迟，2种水稻土浸提液的微生物群落对乳酸盐的利用较差，反应40d后才有明显的Fe（OH）1还原现象在接种铁还原茵的纯培养试验中，磷酸盐浓度在小于1mmol／L或大于16mmol／L时均不能进行铁还原反应，表明铁还原过程对磷酸盐的调控存在浓度阂值．

Effects of Phosphate Concentration on Microbial Iron Reduction

Microbial iron reduction plays an important role on water eutrophication control in the flooded paddy field. However, whether phosphate at high concentration level would inhibit microbial iron reduction is not clear. Slurry anaerobic incubation, synthetic iron oxide system inoculated soil extracts anaerobic culture and inoculated pure iron- reducing bacteria were used as testing methods, by the addition of phosphate at different concentration levels and different carbon sources, to determine proper concentration ranges of phosphorus nutrition for microbial iron reduc- tion. Results showed that in slurry cultivation Fe（ Ⅲ ） reduction rates decreased as phosphorus concentration increased, and Fe（ Ⅱ ） accumulation declined during a later period when the phosphate concentration was at high level. With phosphorus concentration ranging from 4 to 16 mmol/L, the microbial community from Sichuan paddy soil extracts could reduce Fe（llI） rapidly using glucose and pyruvate, while microbial community from Jiangxi paddy soil extracts showed a delayed response to glucose. Two kinds of microbial communities had a slow response to lactate, and there was a significant Fe（OH）3 reduction 40 d after incubation. In the iron-reducing bacteria pure culture test, no iron reduction reaction occurred when phosphorus concentration was less than 1 mmol/L or more than 16 mmol/L, which demonstrated there was a threshold of phosphate concentration on microbial iron reduction.