草鱼肠道微生物群落结构对不同食物的适应性变化机制研究

The gastrointestinal tract of vertebrate is a complex ecosystem where harbors high bacterial diversity. Among its many important functions, the gut microbiota can convert feedstuffs into microbial biomass and fermentation end products that can be utilized by animals, and also can exert on energy metabolism. The stability of the microbial community structure in alimentary canal may thus be very essential for host nutrient digestion and utilization. The grass carp Ctenopharyngodon idellus is a native Chinese freshwater fish with a broad distribution in China. The fish also represents the largest production in Chinese aquaculture. However, hitherto, the knowledge in relation to the microbiome in the grass carp intestine and its role in food digestion is inadequate. In the present study, 16S rRNA gene fingerprinting methods [denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP)] and bar-coded pyrosequencing are employed to determine the dynamic change processes of gut microbial communities of grass carp that are fed on various forages. The aims of the present study are to 1) identify the intestinal bacteria that are associated with food digestion, 2) disclose the building processes of gut microbial communities induced by feed, 3) elucidate the mechanism of changes behind microbial community structures and different forages, and 4) culture the bacteria associated with food digestion, and get bacterial additive which may greatly promote forage digestion. The present study is not only meaningful in theory, but also may improve feed utilization efficiency. The application of the bacterial additive will decrease water pollution made by feed, and promote the healthy development of grass carp forage industry and even Chinese aquaculture.

动物消化道内存在着大量微生物，这些微生物的重要功能之一是参加宿主消化道物质代谢与能量代谢。因此，消化道微生物群落结构的稳定，对于宿主营养物质的消化与吸收至关重要。草鱼是我国淡水养殖产量最大的品种，但是，迄今，对草鱼肠道与食物消化相关微生物的认识还很肤浅。本研究拟以454焦磷酸测序技术为主要手段，通过对摄食不同食物后草鱼肠道微生物群落动态变化过程的比较，全面分析草鱼与食物消化相关的微生物，弄清食物诱导的肠道微生物群落的建立机制，揭示微生物群落结构对不同食物的适应性变化机理。本研究还将根据454测序结果，培养获得与食物消化相关的微生物，通过对表观消化率等指标的分析，阐明微生物促进食物消化的机理，研制与草鱼食物消化相关的高效微生物添加剂。本研究不但具有理论意义，研究成果的应用还能够提高草鱼对饲料的利用效率，减少饲料对水环境的污染，从而促进草鱼饲料工业，乃至我国水产养殖业的健康发展。

动物消化道内存在着大量微生物，这些微生物的重要功能之一是参加宿主消化道物质代谢与能量代谢。因此，消化道微生物群落结构的稳定，对于宿主营养物质的消化与吸收至关重要。草鱼是我国淡水养殖产量最大的品种，但是，迄今为止，对草鱼肠道与食物消化相关微生物的认识还很肤浅。本研究以草鱼为研究对象，通过对摄食不同种食物后草鱼肠道微生物群落结构以及食物转变过程中草鱼肠道微生物群落动态变化的研究，试图全面分析与草鱼食物消化相关的微生物，弄清食物诱导的肠道微生物群落的建立机制，揭示微生物群落结构对不同食物的适应性变化机理。研究发现草鱼肠道中存在着由“变形菌门、厚壁菌门和拟杆菌门”微生物组成的核心微生物，食物转变后草鱼后肠微生物立即发生变化，并且微生物群落在食物转变第11天后再次达到稳定，统计分析显示饲喂鱼粉的后肠微生物与饲喂苏丹草1-33天的后肠微生物存在显著差异（F=10.1, P<0.05），食物转变前后微生物类群由以梭杆菌门细菌（45.8±5.9%）为主转变为以厚壁菌门和拟杆菌门细菌（～90%）为主，说明这些微生物是与食物消化相关的。进一步地根据实验结果，分离培养了与食物消化相关的微生物，得到与纤维素降解相关的兼性厌氧的芽孢杆菌类细菌（Bacillus spp.）以及与蛋白质降解相关的鲸杆菌属细菌（Cetobacterium spp.）。以地衣芽孢杆菌（Bacillus licheniformis）为益生菌的饲喂实验说明地衣芽孢杆菌在提高草鱼存活率，促进草鱼生长方面有明显的作用。鲸杆菌属细菌的研究正在进行中。对草鱼消化道微生物的研究，不但具有重要的理论意义，研究结果还能为今后微生物添加剂的选择及研制提供科学依据，成果的应用还能够提高草鱼对饲料的利用率，减少饲料对水环境的污染，从而促进草鱼饲料工业，乃至我国水产养殖业的健康发展。