College of Resources and Environmental Sciences, China Agricultural University, Beijing, China.
PLoS One. 2012;7(4):e35279. doi: 10.1371/journal.pone.0035279. Epub 2012 Apr 17.
Methanocellales contributes significantly to anthropogenic methane emissions that cause global warming, but few pure cultures for Methanocellales are available to permit subsequent laboratory studies (physiology, biochemistry, etc.).
METHODOLOGY/PRINCIPAL FINDINGS: By combining anaerobic culture and molecular techniques, a novel thermophilic methanogen, strain HZ254(T) was isolated from a Chinese rice field soil located in Hangzhou, China. The phylogenetic analyses of both the 16S rRNA gene and mcrA gene (encoding the α subunit of methyl-coenzyme M reductase) confirmed its affiliation with Methanocellales, and Methanocella paludicola SANAE(T) was the most closely related species. Cells were non-motile rods, albeit with a flagellum, 1.4-2.8 µm long and by 0.2-0.3 µm in width. They grew at 37-60 °C (optimally at 55 °C) and salinity of 0-5 g NaCl l(-1) (optimally at 0-1 g NaCl l(-1)). The pH range for growth was 6.4-7.2 (optimum 6.8). Under the optimum growth condition, the doubling time was 6.5-7.8 h, which is the shortest ever observed in Methanocellales. Strain HZ254(T) utilized H(2)/CO(2) but not formate for growth and methane production. The DNA G+C content of this organism was 52.7 mol%. The sequence identities of 16S rRNA gene and mcrA gene between strain HZ254(T) and SANAE(T) were 95.0 and 87.5% respectively, and the genome based Average Nucleotide Identity value between them was 74.8%. These two strains differed in phenotypic features with regard to substrate utilization, possession of a flagellum, doubling time (under optimal conditions), NaCl and temperature ranges. Taking account of the phenotypic and phylogenetic characteristics, we propose strain HZ254(T) as a representative of a novel species, Methanocella conradii sp. nov. The type strain is HZ254(T) ( = CGMCC 1.5162(T) = JCM 17849(T) = DSM 24694(T)).
CONCLUSIONS/SIGNIFICANCE: Strain HZ254(T) could potentially serve as an excellent laboratory model for studying Methanocellales due to its fast growth and consistent cultivability.
产甲烷杆菌目对造成全球变暖的人为甲烷排放有重要贡献，但可用于后续实验室研究（生理学、生物化学等）的产甲烷杆菌目纯培养物很少。
方法/主要发现：通过结合厌氧培养和分子技术，从中国杭州的一块稻田土壤中分离出了一种新型嗜热产甲烷菌，菌株 HZ254（T）。16S rRNA 基因和 mcrA 基因（编码甲基辅酶 M 还原酶的α亚基）的系统发育分析均证实其与产甲烷杆菌目有关，与 Methanocella paludicola SANAE（T）的亲缘关系最为密切。细胞为非运动杆状，有鞭毛，长 1.4-2.8 µm，宽 0.2-0.3 µm。它们在 37-60°C（最佳温度为 55°C）和 0-5 g NaCl l（最佳温度为 0-1 g NaCl l）下生长。生长的 pH 值范围为 6.4-7.2（最佳 pH 值为 6.8）。在最佳生长条件下，倍增时间为 6.5-7.8 h，这是产甲烷杆菌目中观察到的最短时间。菌株 HZ254（T）利用 H（2）/CO（2）但不利用甲酸盐进行生长和甲烷生成。该生物的 DNA G+C 含量为 52.7 mol%。菌株 HZ254（T）和 SANAE（T）之间 16S rRNA 基因和 mcrA 基因的序列同一性分别为 95.0%和 87.5%，它们之间基于基因组的平均核苷酸同一性值为 74.8%。这两个菌株在底物利用、鞭毛存在、倍增时间（在最佳条件下）、NaCl 和温度范围等方面的表型特征上存在差异。考虑到表型和系统发育特征，我们建议菌株 HZ254（T）作为一个新种的代表，命名为 Methanocella conradii sp. nov.。模式菌株为 HZ254（T）（=CGMCC 1.5162（T）=JCM 17849（T）=DSM 24694（T））。
结论/意义：由于其快速生长和一致的可培养性，菌株 HZ254（T）可能成为研究产甲烷杆菌目的理想实验室模型。
