Bergmann Gaddy T
Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Ramaley N122, Campus Box 334, Boulder, Colorado, 80309-0334, USA.
Cooperative Institute for Research in Environmental Science, University of Colorado, Boulder, Box 216 UCB, Boulder, Colorado, 80309-0216, USA.
BMC Vet Res. 2017 Aug 17;13(1):253. doi: 10.1186/s12917-017-1161-x.
Diversity and composition of microbial communities was compared across the 13 major sections of the digestive tract (esophagus, reticulum, rumen, omasum, abomasum, duodenum, jejunum, ileum, cecum, ascending colon, transverse colon, descending colon, and rectum) in two captive populations of American bison (Bison bison), one of which was finished on forage, the other on grain.
Microbial diversity fell to its lowest levels in the small intestine, with Bacteroidetes reaching their lowest relative abundance in that region, while Firmicutes and Euryarchaeota attained their highest relative abundances there. Gammaproteobacteria were most abundant in the esophagus, small intestine, and colon. The forage-finished bison population exhibited higher overall levels of diversity, as well as a higher relative abundance of Bacteroidetes in most gut sections. The grain-finished bison population exhibited elevated levels of Firmicutes and Gammaproteobacteria. Within each population, different sections of the digestive tract exhibited divergent microbial community composition, although it was essentially the same among sections within a given region of the digestive tract. Shannon diversity was lowest in the midgut. For each section of the digestive tract, the two bison populations differed significantly in microbial community composition.
Similarities among sections indicate that the esophagus, reticulum, rumen, omasum, and abomasum may all be considered to house the foregut microbiota; the duodenum, jejunum, and ileum may all be considered to house the small intestine or midgut microbiota; and the cecum, ascending colon, transverse colon, descending colon, and rectum may all be considered to house the hindgut microbiota. Acid from the stomach, bile from the gall bladder, digestive enzymes from the pancreas, and the relatively low retention time of the small intestine may have caused the midgut's low microbial diversity. Differences in microbial community composition between populations may have been most strongly influenced by differences in diet (forage or grain). The clinical condition of the animals used in the present study was not evaluated, so further research is needed to establish whether the microbial profiles of some bison in this study are indeed indicative of dysbiosis, a predisposing factor to ruminal acidosis and its sequelae.
对两个圈养美洲野牛（Bison bison）群体消化道的13个主要部分（食管、网胃、瘤胃、瓣胃、皱胃、十二指肠、空肠、回肠、盲肠、升结肠、横结肠、降结肠和直肠）的微生物群落多样性和组成进行了比较，其中一个群体以草料育肥，另一个以谷物育肥。
微生物多样性在小肠中降至最低水平，拟杆菌门在该区域的相对丰度降至最低，而厚壁菌门和广古菌门在那里达到最高相对丰度。γ-变形菌纲在食管、小肠和结肠中最为丰富。以草料育肥的野牛群体表现出更高的总体多样性水平，并且在大多数肠道部分中拟杆菌门的相对丰度也更高。以谷物育肥的野牛群体中厚壁菌门和γ-变形菌纲的水平升高。在每个群体中，消化道的不同部分表现出不同的微生物群落组成，尽管在消化道给定区域内的各部分之间基本相同。香农多样性在中肠最低。对于消化道的每个部分，两个野牛群体的微生物群落组成存在显著差异。
各部分之间的相似性表明，食管、网胃、瘤胃、瓣胃和皱胃都可被视为容纳前肠微生物群；十二指肠、空肠和回肠都可被视为容纳小肠或中肠微生物群；盲肠、升结肠、横结肠、降结肠和直肠都可被视为容纳后肠微生物群。来自胃中的酸、胆囊中的胆汁、胰腺中的消化酶以及小肠相对较短的停留时间可能导致了中肠较低的微生物多样性。群体之间微生物群落组成的差异可能受饮食（草料或谷物）差异的影响最大。本研究中使用的动物的临床状况未进行评估，因此需要进一步研究以确定本研究中一些野牛的微生物谱是否确实表明存在生态失调，这是瘤胃酸中毒及其后遗症的一个易感因素。
