Distinctive Responses of Metabolically Active Microbiota to Acidification in a Thermophilic Anaerobic Digester
Distinctive Responses of Metabolically Active Microbiota to Acidification in a Thermophilic Anaerobic Digester
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DOI：
10.1007/s00248-010-9788-1
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发表时间：
2011-04-01
影响因子：
3.6
通讯作者：
Igarashi, Yasuo
中科院分区：
文献类型：
--
作者：
Akuzawa, Masateru;Hori, Tomoyuki;Igarashi, Yasuo
酸化是导致厌氧消化池工艺失败的最常见和最严重的问题之一。挥发性脂肪酸（VFA）的产生主要引发酸休克。然而，对参与产酸代谢过程（如发酵和还原产乙酸）的细菌知之甚少。在这里，产甲烷社区的酸化和由此产生的过程恶化的代谢反应进行了研究，使用转录谱的16S rRNA和甲酰四氢叶酸合成酶（FTHFS）基因。基于16SrRNA的分析表明，细菌种群的动态变化与反应器性能密切相关，特别是与VFA积累水平。pH值的下降伴随着VFAs的增加刺激了未培养的Chloroflexi亚门I细菌的代谢活化。该亚门的特点是作为一个发酵碳水化合物降解使用文化和分子为基础的生态生理学测定。在开始的VFA积累，FTHFS基因表达的成绩单是来自遗传学预测homoacetogenes，这表明，还原产乙酸操作迄今不明的细菌。当乙酸浓度高时，FTHFS表达停止，嗜酸热厌氧杆菌选择性增殖。这种嗜热嗜酸菌在通过发酵代谢生产乙酸中起决定性作用。本研究结果首次揭示了未培养的绿弯藻T. aciditolerans，和新的homoacetogenes代谢与酸休克和随后的VFA积累在厌氧消化器。
Acidification is one of the most common and serious problems inducing process failure in anaerobic digesters. The production of volatile fatty acids (VFAs) mainly triggers acidic shock. However, little is known about the bacteria involved in the processes of acidogenic metabolism, such as fermentation and reductive acetogenesis. Here, the metabolic responses of a methanogenic community to the acidification and resulting process deterioration were investigated using transcriptional profiling of both the 16S rRNA and formyltetrahydrofolate synthetase (FTHFS) genes. The 16S rRNA-based analyses demonstrated that the dynamic shift of bacterial populations was closely correlated with reactor performance, especially with VFA accumulation levels. The pH drop accompanied by an increase in VFAs stimulated the metabolic activation of an uncultured Chloroflexi subphylum I bacterium. The subphylum has been characterized as a fermentative carbohydrate degrader using culture- and molecular-based ecophysiological assays. At the beginning of VFA accumulation, FTHFS genes were expressed; the transcripts were derived from phylogenetically predicted homoacetogens, suggesting that reductive acetogenesis was operated by hitherto unidentified bacteria. When acetate concentrations were high, the FTHFS expression ceased and Thermoanaerobacterium aciditolerans proliferated selectively. This thermoacidophilic bacterium would play a decisive role in acetate production via fermentative metabolism. The results of this study reveal for the first time that an uncultured Chloroflexi, T. aciditolerans, and novel homoacetogens were metabolically associated with acidic shock and subsequent VFA accumulation in an anaerobic digester.