Kosaka Tomoyuki, Toh Hidehiro, Fujiyama Asao, Sakaki Yoshiyuki, Watanabe Keiji, Meng Xian-Ying, Hanada Satoshi, Toyoda Atsushi
Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, 753-8515, Japan; PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012, Japan; Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan.
Environ Microbiol Rep. 2014 Jun;6(3):268-77. doi: 10.1111/1758-2229.12128. Epub 2013 Dec 12.
Several thermophilic hydrogenotrophic methanogens naturally aggregate in their habitats in association with hydrogen-producing bacteria for efficient transfer of the methane fermentation intermediates to produce methane. However, physiology of aggregation and the identity of aggregation-specific genes remain to be elucidated. Here, we isolated and characterized a hydrogen and formate-utilizing Methanothermobacter sp. CaT2 that is capable of self-aggregation and utilizing formate. CaT2 produced methane from propionate oxidation in association with a syntrophic propionate-oxidizing bacterium faster than other methanogens, including Methanothermobacter thermautotrophicus ΔH and Methanothermobacter thermautotrophicus Z-245. CaT2 also aggregated throughout the culture period and was coated with polysaccharides, which was not found on the ΔH and Z-245 cells. Sugar content (particularly of rhamnose and mannose) was also higher in the CaT2 cells than the ΔH and Z-245 cells. Comparative genomic analysis of CaT2 indicated that four candidate genes, all of which encode glycosyltransferase, were involved in aggregation of CaT2. Transcriptional analysis showed that one glycosyltransferase gene was expressed at relatively high levels under normal growth conditions. The polysaccharide layer on the CaT2 cell surface, which is probably assembled by these glycosyltransferases, may be involved in cell aggregation.
几种嗜热氢营养型产甲烷菌在其栖息地自然聚集，与产氢细菌共生，以有效转移甲烷发酵中间体来产生甲烷。然而，聚集的生理机制以及聚集特异性基因的身份仍有待阐明。在此，我们分离并鉴定了一种利用氢气和甲酸盐的嗜热栖热甲烷杆菌属菌株CaT2，它能够自我聚集并利用甲酸盐。与同营养丙酸氧化细菌共生时，CaT2从丙酸盐氧化中产生甲烷的速度比其他产甲烷菌更快，包括嗜热自养甲烷杆菌ΔH和嗜热自养甲烷杆菌Z - 245。在整个培养期间，CaT2也会聚集，并且表面覆盖有多糖，而在ΔH和Z - 245细胞上未发现这种情况。CaT2细胞中的糖含量（特别是鼠李糖和甘露糖）也高于ΔH和Z - 245细胞。对CaT2的比较基因组分析表明，四个候选基因均编码糖基转移酶，它们参与了CaT2的聚集过程。转录分析表明，在正常生长条件下，一个糖基转移酶基因表达水平相对较高。CaT2细胞表面的多糖层可能由这些糖基转移酶组装而成，可能参与细胞聚集。
