Islam Tajul, Jensen Sigmund, Reigstad Laila Johanne, Larsen Oivind, Birkeland Nils-Kåre
Department of Biology and Centre for Geobiology, University of Bergen, P.O. Box 7800, N-5020 Bergen, Norway.
Proc Natl Acad Sci U S A. 2008 Jan 8;105(1):300-4. doi: 10.1073/pnas.0704162105. Epub 2008 Jan 2.
Methanotrophic bacteria constitute a ubiquitous group of microorganisms playing an important role in the biogeochemical carbon cycle and in control of global warming through natural reduction of methane emission. These bacteria share the unique ability of using methane as a sole carbon and energy source and have been found in a great variety of habitats. Phylogenetically, known methanotrophs constitute a rather limited group and have so far only been affiliated with the Proteobacteria. Here, we report the isolation and initial characterization of a nonproteobacterial obligately methanotrophic bacterium. The isolate, designated Kam1, was recovered from an acidic hot spring in Kamchatka, Russia, and is more thermoacidophilic than any other known methanotroph, with optimal growth at approximately 55 degrees C and pH 3.5. Kam1 is only distantly related to all previously known methanotrophs and belongs to the Verrucomicrobia lineage of evolution. Genes for methane monooxygenases, essential for initiation of methane oxidation, could not be detected by using standard primers in PCR amplification and Southern blot analysis, suggesting the presence of a different methane oxidation enzyme. Kam1 also lacks the well developed intracellular membrane systems typical for other methanotrophs. The isolate represents a previously unrecognized biological methane sink, and, due to its unusual phylogenetic affiliation, it will shed important light on the origin, evolution, and diversity of biological methane oxidation and on the adaptation of this process to extreme habitats. Furthermore, Kam1 will add to our knowledge of the metabolic traits and biogeochemical roles of the widespread but poorly understood Verrucomicrobia phylum.
甲烷氧化细菌是一类广泛存在的微生物，在生物地球化学碳循环以及通过自然减少甲烷排放来控制全球变暖方面发挥着重要作用。这些细菌具有独特的能力，能够将甲烷作为唯一的碳源和能源，并且已在各种各样的栖息地中被发现。从系统发育角度来看，已知的甲烷氧化菌构成了一个相当有限的群体，迄今为止仅与变形菌门有关联。在此，我们报告了一种非变形菌门专性甲烷氧化细菌的分离及初步特性描述。该分离菌株被命名为Kam1，是从俄罗斯堪察加半岛的一个酸性温泉中分离得到的，它比任何其他已知的甲烷氧化菌更嗜热嗜酸，在约55摄氏度和pH值3.5的条件下生长最佳。Kam1与所有先前已知的甲烷氧化菌亲缘关系都很遥远，属于疣微菌门进化谱系。在PCR扩增和Southern印迹分析中，使用标准引物无法检测到甲烷单加氧酶基因，而甲烷单加氧酶对于启动甲烷氧化至关重要，这表明存在一种不同的甲烷氧化酶。Kam1还缺乏其他甲烷氧化菌典型的发育良好的细胞内膜系统。该分离菌株代表了一个此前未被认识的生物甲烷汇，并且由于其不寻常的系统发育归属，它将为生物甲烷氧化的起源、进化和多样性以及这一过程对极端栖息地的适应性提供重要线索。此外，Kam1将增进我们对广泛但了解甚少的疣微菌门的代谢特征和生物地球化学作用的认识。
