瘤胃甲烷菌第七目的研究进展

随着测序技术和体外培养技术的进步,越来越多的未知甲烷菌被发现。近年来,第七个甲烷菌目"Methanomassiliicoccales"(简称Mmc)被发现并建立。这一目甲烷菌在进化关系上与热原体古菌相近,但又存在较远距离,独立成簇。Mmc分布广泛,遍布哺乳动物和昆虫的消化道以及稻田、湿地等环境,但不同来源菌株表现出生境偏好性。Mmc缺少将CO2还原为甲基辅酶M的完整代谢途径,导致它们严格利用氢气还原甲基底物生成甲烷。全面深入地了解Mmc在反刍动物瘤胃中发挥的功能,将有助于新型高效反刍动物甲烷减排策略的提出。因此,本文主要综述了Mmc菌株的分离培养、生理生化和基因组特性及其在瘤胃甲烷生成中的作用。

Progress of Methanomassiliicoccales in the rumen

With the development of sequencing and in vitro culture technique, more and more unknown methanogens have been identified. In recent years, the 7^th order of methanogen (Methanomassiliicoccales, Mmc) has been gradually discovered and established. Mmc is close to Thermoplasmatales in evolutionary ralationship, but it exists at a relatively long distance and forms an independent cluster. Mmc is widely distributed in the digestive tract of mammalian and insects, paddy fields, wetlands and other environments, but strains from different environments exhibit habitat preference. Mmc lacks the complete metabolic pathway to reduce CO₂ to methyl coenzyme M, which leads to their strict use of hydrogen to reduce methyl substrates to genetrate methane. A comprehensive and in-depth understanding of the functions of Mmc in rumen of ruminants will be conducive to the proposal of a new and efficient strategy for methane emission reduction in ruminants. Therefore, we review here the isolation culture, physiochemical and genomic properties of Mmc as well as its role in the rumen methane production.