Mcroorgarisms composing synlrophic melhanoseric communly in paddy fieidsoil

本研究采用培养方法和分子生态学技术对稻田土壤中组成互养型产甲烷菌群落的微生物进行了研究。以丙酸盐和乙酸盐为基质，接种稻田土壤，对产甲烷菌进行富集培养，并对培养物中的微生物群落进行了研究。用变性梯度凝胶电泳法从丙酸盐培养基中分离到一个与产醋酸蛋白菌（Proteiniphilumacetatigenes）密切相关的DNA片段。单独的产乙酸假单胞菌不降解丙酸盐也不产生甲烷，但当细菌共存于丙酸盐氧化互养培养物中时，刺激丙酸盐的降解和甲烷生成。结果表明，稻田土壤中可能存在类似的互养作用。甲烷八叠球菌或甲烷杆菌样产甲烷古菌和细菌占主导地位的乙酸文化。从富集培养物中分离到一株产氢甲烷菌AH1和一株硫酸盐还原菌Desulfovibrio sp. Al。共培养的菌株AH1和A1降解丙酮酸，乳酸和乙醇为甲烷，表明氢营养型产甲烷菌和硫酸盐还原剂在稻田土壤中的产甲烷互养协会。然而，共培养物不能将乙酸盐降解为甲烷，并且不能证明互养乙酸盐氧化

The objective of the present research project was to characterize microorganisms composing syntrophic methanogenic community in paddy field soil by the cultivation method and molecular ecological techniques. Methanogenic cultures were enriched on propionate and acetate inoculated with paddy field soil and the microbial communities in the cultures were examined. A DNA fragment closely related to Proteiniphilum acetatigenes was obtained from the culture on propionate by the denaturing gradient gel electrophoresis method. P. acetatigenes alone does not degrade propionate nor produce methane, but stimulates degradation of propionate and methanogenesis when the bacterium coexists in the propionate oxidizing syntrophic culture. The results suggested that similar syntrophic interaction may have functioned in the paddy field soil. Methanosarcina- or Methanobacterium-like methanogenic archaea and a bacterium were predominated in the culture on acetate. A hydrogenotrophic methanogenic strain, Methanobacterium sp. AH1, and a sulfate reducer, Desulfovibrio sp. Al, were isolated from the enrichment culture. Co-culture of strains AH1 and A1 degraded pyruvate, lactate and ethanol to methane, indicating syntrophic association of hydrogenotrophic methanogens and sulfate reducers for methanogenesis in paddy field soil. However, the co-culture did not degrade acetate to methane and syntrophic acetate oxidation could not be demonstrated