Characterization of methanogens and their key genes associated with methane production in beef cattle: linkage to host performance

反刍动物与瘤胃微生物之间存在着共生关系，反刍动物采食饲料的微生物发酵在补充牛代谢功能的能量方面起着重要作用。牛的瘤胃是一个活跃的生物反应器，产生许多未知的生物产物，是牛日常营养吸收、生产和健康维持的基本组成部分。迄今为止，对瘤胃中微生物的生物学过程的理解是不够的，并且微生物功能与宿主性能（例如，甲烷产生）之间的联系还没有被很好地理解。甲烷气体是由一组古生菌（产甲烷菌）在瘤胃中微生物分解有机物质的最终产物。据估计，反刍动物产生的甲烷约占大气排放总量的15%。本研究旨在探讨生态瘤胃产甲烷菌及其所产酶与肉牛产甲烷特性的关系。首先，将使用不依赖培养的方法研究瘤胃中甲烷菌的多样性。其次，通过测定甲烷生物合成关键基因的遗传和表达变异，分析其功能。最后，本研究将探讨产甲烷菌及上述关键酶在一组不同饲粮条件下的作用，以阐明其与肉牛甲烷产生的关系。 本研究的长期目标是提供一个研究计划，可以阐明瘤胃微生物的生物学功能和宿主表型性能之间的关系，并应用这些知识来改善宿主的生产和健康性状。

It is well known that ruminants and ruminal microorganisms have a symbiotic relationship which microbial fermentation of ingested feed plays a major role in supplement of energy for metabolic functions in cattle. The rumen of cattle can be considered as an active "bio-reactor" producing many unknown bio-products, which are fundamental components for cattle's daily nutrition uptake, production, and health maintenance. Up to date, the understanding of the biological process of microbes in the rumen is insufficient and the linkage between the microbial functions with host's performance, for example, methane production, has not been well understood. Methane gas is the end product of the microbial decomposition of organic matter in the rumen by a group of archaea, the methanogens. It has been estimated that methane production by ruminants is about 15% of total atmospheric emissions. The aim of this study is to investigate the association between the ecology ruminal methanogens and their produced enzymes with the methane production trait of beef cattle. Firstly, the diversity of methanogens in the rumen will be investigated using culture independent methods. Secondly, functions of microbial key genes in the methane biosynthesis will be analyzed by the measurement of their genetic and expression variations. Last, the roles of methanogens and the above key enzymes will be investigated in a group of animals under different diets to elucidate their relationships to the methane production in beef cattle. The long-term goal of this study is to deliver a research program that can elucidate the associations between the biofunctions of rumen microbes and host phenotypical performance, and to apply the knowledge to improve host's production and health traits.