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

众所周知，反刍动物和瘤胃微生物之间存在着共生关系，在牛的代谢功能中，饲料微生物发酵对能量的补充起主要作用。牛的瘤胃可以被认为是一个活跃的“生物反应器”，产生许多未知的生物产品，这些产品是牛日常营养吸收、生产和健康维护的基本成分。到目前为止，对瘤胃微生物的生物学过程的了解还不够充分，微生物的功能与宿主的表现之间的联系，例如甲烷生产，还没有被很好地理解。甲烷气体是一群古生菌(产甲烷菌)对瘤胃内有机物进行微生物分解的最终产物。据估计，反刍动物产生的甲烷约占大气总排放量的15%。本研究旨在探讨瘤胃产甲烷菌及其产酶与肉牛产甲烷性状的关系。首先，将使用非培养的方法调查瘤胃中产甲烷菌的多样性。其次，通过对微生物关键基因的遗传和表达变异的测量，分析微生物关键基因在甲烷生物合成中的功能。最后，将研究甲烷菌和上述关键酶在不同日粮下对一组动物的作用，以阐明它们与肉牛甲烷产量的关系。这项研究的长期目标是提供一项研究计划，以阐明瘤胃微生物的生物功能与宿主表型表现之间的关系，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.