Analysis on the metabolism network of volatile fatty acids by methanogenic consortia

利用<-1><-1>~（13）<13>C标记的乙酸盐和气相色谱-质谱（GC-MS）联用技术，研究了产甲烷菌群在稀释率为0.025d ~ 2和0.6d ~ 2的乙酸盐恒化器中的乙酸盐转化途径。在低稀释率下，乙酸盐氧化互养体和氢营养型产甲烷菌的非乙酸盐互养氧化被认为是总产甲烷的主要途径。甲基辅酶M还原酶基因（merA）转录物的系统发育分析证实，在低稀释率和高稀释率下，恒化器中存在大量的甲烷八叠球菌属（Methanoculleus，hydrogenotrophic methanogens）和甲烷八叠球菌属（Methanosarcina，aceticaceticacetylogens）的转录物，分别乙酸甲烷菌属的mcrA转录本 关于我们 由于所用引物的有限多样性覆盖，在两种稀释率下都很难检测到占群体优势的TIC产甲烷菌。采用<-1>荧光原位杂交（FISH）、变性梯度凝胶电泳（DGGE）和16 SrDNA克隆分析等方法，研究了稀释率为0.01和0.3d ^时丙酸盐恒化器中产甲烷菌群的群落结构.在该领域的微生物，密切相关的属Methanosaeta和Methanoculleus被证明是占主导地位的低稀释率。在细菌中，丙酸盐氧化互养体Syntrophic被证明是占主导地位的。在高稀释率下，甲烷菌属（Methanosaeta）、甲烷菌属（Methanoculleus）和甲烷菌属（Methanoaculllum）的微生物在菌群中占优势。在细菌中，与脱硫肠状菌属相关的微生物占主导地位。这些结果表明，负责降解丙酸盐的微生物因稀释率而异。少

Acetate conversion pathways of methanogenic consortia in acetate-fed chemostats at dilution rates of 0.025 d^<-1> and 0.6 d^<-1> were investigated using ^<13>C-labeled acetates followed by gas chromatogram mass spectrometry (GC-MS) analysis of CH_4 and CO_2 produced. Non-aceticlastic syntrophic oxidation by acetate oxidizing syntrophs and hydrogenotrophic methanogens was suggested to occupy a primary pathway in total methanogenesis at the low dilution rate. In contrast, aceticlastic cleavage of acetate by aceticlastic methanogens was suggested to occupy a primary pathway in total methanogenesis at the high dilution rate.Phylogenetic analyses of transcripts of the methyl coenzyme M reductase gene (merA) confirmed a significant number of transcripts of the genera Methanoculleus, hydrogenotrophic methanogen, and Methanosarcina, aceticlastic methanogen, were present in the chemostats at the low and high dilution rates, respectively. The mcrA transcripts of the genus Methanosaeta, aceticlas … More tic methanogen, which dominated the population, were poorly detected at the both dilution rate due to the limited diversity coverage of the primers used. These results demonstrated that dilution rate could cause a shift in the primary pathway of acetate conversion to methane in acetate-fed chemostats.The microbial communities of methanogenic consortia in propionate-fed chemostats at dilution rates of 0.01 and 0.3 d^<-1> were investigated using fluorescence in situ hybridization (FISH), denaturing gradient gel electrophoresis (DGGE) and 16S rDNA clone analysis. In the domain Archaea, microorganisms closely related to the genera Methanosaeta and Methanoculleus were shown to be predominant at the low dilution rate. In the domain Bacteria, a propionate-oxidizing syntroph Syntrophobacter was shown to be predominant. At the high dilution rate, microorganisms related to the genera Methnaosaeta, Methanoculleus, Methanospirillum were dominant in the domain Archaea. In the domain Bacteria, microorganisms related to the genus Desulfotomaculum were predominant. These results indicated that the microorganisms responsible for degradation of propionate were different by the dilution rates. Less