Table_1_The Effects of Unfermented and Fermented Cow and Sheep Milk on the Gut Microbiota.XLSX

A variety of fermented foods have been linked to improved human health, but their impacts on the gut microbiome have not been well characterized. Dairy products are one of the most popular fermented foods and are commonly consumed worldwide. One area we currently lack data on is how the process of fermentation changes the gut microbiota upon digestion. What is even less well characterized are the possible differences between cow and other mammals’ milks. Our aim was to compare the impact of unfermented skim milk and fermented skim milk products (milk/yogurt) originating from two species (cow/sheep) on the gut microbiome using a rat model. Male Sprague-Dawley rats were fed a dairy-free diet supplemented with one of four treatment dairy drinks (cow milk, cow yogurt, sheep milk, sheep yogurt) for 2 weeks. The viable starter culture bacteria in the yogurts were depleted in this study to reduce their potential influence on gut bacterial communities. At the end of the study, cecal samples were collected and the bacterial community profiles determined via 16S rRNA high-throughput sequencing. Fermentation status drove the composition of the bacterial communities to a greater extent than their animal origin. While overall community alpha diversity did not change among treatment groups, the abundance of a number of taxa differed. The cow milk supplemented treatment group was distinct, with a higher intragroup variability and a distinctive taxonomic composition. Collinsella aerofaciens was of particularly high abundance (9%) for this group. Taxa such as Firmicutes and Lactobacillus were found in higher abundance in communities of rats fed with milk, while Proteobacteria, Bacteroidetes, and Parabacteroides were higher in yogurt fed rats. Collinsella was also found to be of higher abundance in both milk (vs. yogurt) and cows (vs. sheep). This research provides new insight into the effects of unfermented vs. fermented milk (yogurt) and animal origin on gut microbial composition in a healthy host. A number of differences in taxonomic abundance between treatment groups were observed. Most were associated with the effects of fermentation, but others the origin species, or in the case of cow milk, unique to the treatment group. Future studies focusing on understanding microbial metabolism and interactions, should help unravel what drives these differences.

多种发酵食品均被证实可改善人体健康，但其对肠道微生物组（gut microbiome）的调控效应尚未得到充分解析。乳制品是全球最受欢迎的发酵食品品类之一，受众遍及全球。当前我们仍缺乏关于发酵过程如何在消化阶段调控肠道微生物群（gut microbiota）的相关数据，而牛乳与其他哺乳动物乳汁之间的潜在差异，更是鲜有研究涉及。本研究旨在借助大鼠模型，对比源自两种哺乳动物（牛、绵羊）的未发酵脱脂乳与发酵脱脂乳制品（牛乳/羊乳酸奶）对肠道微生物组的影响。选取雄性斯普拉格-道利（Sprague-Dawley）大鼠，以无乳制品日粮喂养，同时分别添加四种试验乳制品饮品（牛乳、牛乳酸奶、羊乳、羊乳酸奶），持续干预2周。本研究中对酸奶中的活性发酵剂活菌进行了灭活处理，以降低其对肠道细菌群落的潜在干扰。试验结束后采集盲肠样本，通过16S rRNA高通量测序分析细菌群落结构。相较于乳汁来源的哺乳动物种类，发酵状态对细菌群落组成的影响更为显著。尽管各组的群落整体α多样性无显著差异，但多个分类单元（taxa）的相对丰度存在明显区别。牛乳添加组的群落结构具有显著特异性，其组内变异度更高，且分类单元组成独具特征。该组中产气柯林斯菌（Collinsella aerofaciens）的相对丰度尤为突出，可达9%。在喂食乳类的大鼠肠道菌群中，厚壁菌门（Firmicutes）、乳杆菌属（Lactobacillus）等分类单元的相对丰度显著升高；而喂食酸奶的大鼠肠道菌群中，变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）以及副杆菌属（Parabacteroides）的相对丰度更高。柯林斯菌属（Collinsella）在乳类（相较于酸奶）以及牛乳来源（相较于羊乳）的样本中，相对丰度均显著升高。本研究为解析未发酵/发酵乳类及乳汁来源对健康宿主肠道微生物群落组成的影响提供了全新视角。本研究观察到各组间分类单元相对丰度存在多处差异：多数差异与发酵过程相关，其余差异则源自乳汁来源物种的不同，而牛乳添加组的差异则具有组特异性。未来针对微生物代谢与互作机制的研究，将有助于阐明造成上述差异的核心驱动因素。