四种不同食性鱼类肠道微生物群落组成及多样性比较分析

本研究旨在探讨食性对鱼类肠道菌群组成和多样性的影响，并预测特定菌群对不同营养素的潜在功能。实验采用高通量16S rRNA基因测序技术，提取获得滇池高背鲫(Carassius auratus)、草鱼(Ctenopharyngodon idellus)、鳜鱼(Siniperca chuatsi)、昆明裂腹鱼(Shizothorax grahami) 4种不同食性鱼类的肠道内容物，12个样品的16S rRNA，构建文库并测序，分析这4种鱼类肠道微生物的菌落组成和多样性。结果显示，鱼类肠道菌群多样性受到食性的显著影响(P<0.05)，综合表现为杂食性(滇池高倍鲫) > 草食性(草鱼) > 滤食性(昆明裂腹鱼) > 肉食性(鳜鱼)。4种鱼类具有一些相同的优势菌群：变形菌门(Proteobacteria)和厚壁菌门(Firmicutes)。然而，优势菌群在属水平上存在一定差异，如不动杆菌属(Acinetobacter)为鳜鱼的优势菌群，拟杆菌属(Bacteroides)为草鱼的优势菌群等。功能预测发现，鳜鱼肠道中以革兰氏阴性菌为主；草鱼抗病潜力略高于其他3种鱼类；约氏不动杆菌(A._ johnsonii)、鲁氏不动杆菌(A. lwoffii)和施氏假单胞菌(Pseudomonas stutzeri)可能有助于宿主对蛋白质的消化，而拟杆菌属中的某些菌群可能有助于宿主消化纤维素。综上所述，食性是影响鱼类肠道菌群组成和多样性差异化的主要因素之一，分析食性与肠道优势菌群之间的关联，探讨特异菌群的功能，可为研究鱼类营养代谢的微生物效应奠定理论基础。

Comparative analysis of the composition and diversity of the intestinal microflora of four fishes with different feeding habits

Fish are generally classified as herbivorous, carnivorous, omnivorous, or filter-feeders according to feeding habits, including the feeding method and food content. The feeding habits of fish are reflected in their digestive organ, mainly the intestine. The intestine tract is the main site for digestion and nutritional uptake, and it is regarded as a key organ in fish nutrition. Reportedly, fish gut microbiota contributes to digestion and affect gastrointestinal tract development as well as the overall growth of the fish. The disruption of the intestinal microbiota induced by their feeding habit via diet usually affects the digestive functions of the host through disturbance in bacterial digestive enzyme production. Feeding habits determine the feed composition, which shapes the microbial communities in fish. For example, diet has been reported as a dominant cause of variation in the microbiota composition of rainbow trout. In contrast, feeding habit, which is regulated by many factors, including intrinsic and external factors, such as appetite, structure of the digestive tract, and feed palatability, is an important area of research in the intestinal microflora study. The feeding habit of fishes is one of the main factors affecting the differential colonization of fish intestinal flora. For example, the feeding habit increases the colonization of fish intestinal flora in the order omnivorous > herbivorous > carnivorous. It is also known that feeding habits influence intestinal digestion and structure. However, the influence of feeding habit on proximate composition, digestive enzyme secretion, and intestinal histomorphology is currently not well-known in fish. On the contrary, the feeding habit affects the composition and diversity of the intestinal microflora of fish. The composition and diversity of the microbiota in Carassius auratus, Ctenopharyngodon idella, Siniperca chuatsi, and Schizothorax grahami from the same environment have also not previously been studied. The present study aimed to compare and analyze the differences in the composition and diversity of the intestinal microflora of four fish species, investigating the relationship between their feeding habits and intestinal microflora as well. This study collected 12 intestine samples from each of the four fishes with different feeding habits, including omnivorous (C. auratus), herbivorous (C. idella), filter-feeder (S. chuatsi), and carnivorous (S. grahami), from the same pond. The composition and diversity of the microbial communities were determined by using high-throughput sequencing of 16S rRNA. Meanwhile, this study investigated the effects of feeding habits on the composition and diversity of the intestinal microflora of fish and predicted the potential functions of specific microflora with different nutrients. The results showed that the diversity of the intestinal microflora in fish was significantly affected by feeding habit (P<0.05), such that higher levels occurred in the order omnivorous (C. auratus) > herbivorous (C. idella) > filter-feeder (S. grahami) > carnivorous (S. chuatsi). Proteobacteria and Firmicutes were the common dominant flora among the four fishes, although there were differences at the genera and species levels. For example, Acinetobacter and Bacteroides species were the most dominant flora in S. chuatsi and C. idella, respectively. Function prediction showed that the intestinal tract of S. chuatsi was mainly gram-negative. The disease resistance potential of C. idella was slightly higher than that of the other three fish species. Acinetobacter johnsonii, Acinetobacter lwoffii, and Pseudomonas stutzeri might help the host to digest protein, while Bacteroidetes may help the host to digest cellulose. In conclusion, feeding habit is one of the main factors affecting the differential colonization of fish intestinal flora. Analyzing the correlation between feeding habits and dominant intestinal flora as well as exploring the function of specific flora, could lay a theoretical foundation for studying the microbial effect of fish nutrition metabolism.