Novel Syntrophic Isovalerate-Degrading Bacteria and Their Energetic Cooperation with Methanogens in Methanogenic Chemostats
Novel Syntrophic Isovalerate-Degrading Bacteria and Their Energetic Cooperation with Methanogens in Methanogenic Chemostats
复制标题
新型共养异戊酸降解细菌及其与产甲烷恒化器中产甲烷菌的能量合作
DOI：
10.1021/acs.est.0c01840
复制
发表时间：
2020-08-04
影响因子：
11.4
通讯作者：
Tang, Yue-Qin
中科院分区：
文献类型：
--
作者：
Chen, Ya-Ting;Zeng, Yan;Tang, Yue-Qin
异戊酸是蛋白质/氨基酸厌氧降解的重要中间体。由于异戊酸降解细菌的培养和表征面临挑战，人们对这种化合物如何降解知之甚少，这种细菌被认为与产甲烷古菌共生。在这项研究中，我们成功地丰富了新的互养异戊酸降解菌（未培养的梭菌目和互养科成员）通过操作嗜温和嗜热异戊酸进料厌氧反应器。基于宏基因组学和元转录组学的新型推定互养异戊酸代谢者的代谢重建揭示了分解代谢途径和副产物（即，乙酸盐、H-2和甲酸盐）、从异戊酸盐降解到H-2和甲酸盐产生的电子转导机制（通过电子转移黄素蛋白; ETF）和生物合成代谢。所确定的生物体倾向于更喜欢甲酸盐为基础的种间电子转移与产甲烷的合作伙伴。副产物乙酸盐通过甲烷丝菌属（嗜温）和甲烷八叠球菌属（嗜热）进一步转化为CH 4和CO2，这两种菌采用不同的乙酸盐降解方法。这项研究提出了新的嗜温和嗜热异戊酸降解菌及其与产甲烷菌的相互作用的见解。
Isovalerate is an important intermediate in anaerobic degradation of proteins/amino acids. Little is known about how this compound is degraded due to challenges in cultivation and characterization of isovalerate-degrading bacteria, which are thought to symbiotically depend on methanogenic archaea. In this study, we successfully enriched novel syntrophic isovalerate degraders (uncultivated Clostridiales and Syntrophaceae members) through operation of mesophilic and thermophilic isovalerate-fed anaerobic reactors. Metagenomics- and metatranscriptomics-based metabolic reconstruction of novel putative syntrophic isovalerate metabolizers uncovered the catabolic pathway and byproducts (i.e., acetate, H-2, and formate) of isovalerate degradation, mechanisms for electron transduction from isovalerate degradation to H-2 and formate generation (via electron transfer flavoprotein; ETF), and biosynthetic metabolism. The identified organisms tended to prefer formate-based interspecies electron transfer with methanogenic partners. The byproduct acetate was further converted to CH4 and CO2 by either Methanothrix (mesophilic) and Methanosarcina (thermophilic), which employed different approaches for acetate degradation. This study presents insights into novel mesophilic and thermophilic isovalerate degraders and their interactions with methanogens.