Analysis on Inter-Cell Electron Transport Systems of Microbial Community in Anaerobic Bioreactor

在产甲烷条件下，具有不同代谢能力的微生物对复杂有机物进行一系列的代谢降解。有几个反应步骤，其中涉及细菌和Arcahea之间的合养联系。虽然这一系统还不清楚，但基于种间电子传递系统，已经部分解释了这些合养联合的机制。在这项研究中，我们构建了降解(I)乙酸盐、(II)丙酸或(III)牛血清白蛋白(BSA)的富含产甲烷菌群的中温厌氧恒化器培养。利用这些化学抑制剂，我们分析了微生物群落结构，以了解降解这些底物的合养关联和种间电子传递系统。利用RT-PCR和^&lt；13&gt；C标记的乙酸酯分析了乙酸酯的转化途径。在低稀释率为0.025 d^~(-1)~(-1)~(-1)的条件下，乙酸酯氧化合营养菌和产氢产甲烷菌在总产甲烷中占据主要途径。在丙酸降解恒化器中，在0.01d^~(-1)的低稀释率和0.3d^~(-1)~(-1)的高稀释率下，合养细菌近缘与甲烷球藻和/或甲烷螺杆菌共生，并在丙酸降解恒化器中起中心作用。在降解牛血清白蛋白的恒化器中，氨杆菌属可能与甲烷假单胞菌共生，并在添加镍和钴的条件下在氨基酸降解中发挥核心作用，从而增加产甲烷古生菌的数量。

Under methanogenic conditions, complex organic matters are degraded in a series metabolism by a number of microorganisms of different metabolic abilities. There are several reaction steps, where syntrophic associations between Bacteria and Arcahea are involved. The mechanism of these syntrophic associations has been partly explained based on interspecies electron transport system, although this system remains unknown in detail. In this study we constructed mesophilic anaerobic chemostat cultivations of enriched methanogenic consortia degrading (i) acetate, (ii) propionate or (iii) bovine serum albmin (BSA). Using these chemostats, we analyzed the microbial community structures to understand the syntrophic associations for degrading these substrates and the interspecies electron transport system.Acetate conversion pathway was analyzed using RT-PCR and ^<13>C-labeled acetates. Syntrophic oxidation by acetate oxidizing syntrophs belonging to Firmicutes and hydrogenotrophic methanogens Methanoculleus was suggested to occupy a primary pathway in total methanogenesis at the low dilution rate of 0.025 d^<-1>. In the propionate degradation chemostat, Syntrophobacter relatives and Pelotomaculum relatives were suggested to syntrophically associate with Methanoculleus and/or Methanospirillum and to play the central roles for propionate degradation at the low dilution rate of 0.01 d^<-1> and the high dilution rate of 0.3 d^<-1>, respectively. In the BSA-degrading chemostat, the genus Aminobacterium, was suggested to associate with Methanoculleus and play a central role in amino acid degradation under the condition of Ni^<2+> and Co^<2+> addition, which allowed increased population of methanogenic Archaea.