背景:肠道微生物群(GM)与导致短链脂肪酸(SCFA)产生的膳食成分代谢之间的相互作用受到一系列因素的影响,包括结肠pH和碳水化合物来源。然而,关于胃肠道中的GM活性和代谢物产生如何受pH和pH梯度沿结肠增加的影响的知识仍然有限。
结果:在这里,我们研究了与结肠中通常发现的水平相对应的pH梯度对使用底物菊粉的GM组成和代谢物产生的影响,乳糖,低聚半乳糖(GOS),和低聚果糖(FOS)在体外结肠设置中。我们研究了3种不同的pH条件(低,5.2增加到6.4;中等,5.6增加到6.8和高,6.0增加到7.2)对于每个粪便接种物,并且发现结肠pH梯度显着影响体外模拟的GM结构,但粪便供体和底物的影响更为明显。低pH条件强烈影响GM,拟杆菌属的相对丰度降低。和增加双歧杆菌。较高的体外模拟结肠pH以供体和底物依赖性方式促进SCFA的产生。丁酸生产者在较高的pH条件下富集,菊粉的丁酸盐产量也增加了。相低温杆菌属的相对丰度,拟杆菌,和Rikenellaceae也在较高的结肠pH下增加,伴随着以GOS和FOS为底物的丙酸盐产量增加。
结论:一起,我们的结果表明,结肠底物,如膳食纤维影响转基因成分和代谢产物的生产,不仅被特定的微生物选择性地利用,但也因为他们的SCFA生产,这反过来也会影响结肠pH和整体GM组成和活性。我们的工作提供了有关从近端到远端结肠的pH上升梯度对体外发酵饮食底物的影响的详细信息,并强调了在转基因研究中考虑pH的重要性。
BACKGROUND: The interplay between gut microbiota (GM) and the metabolization of dietary components leading to the production of short-chain fatty acids (SCFAs) is affected by a range of factors including colonic pH and carbohydrate source. However, there is still only limited knowledge on how the GM activity and metabolite production in the gastrointestinal tract could be influenced by pH and the pH gradient increases along the colon.
RESULTS: Here we investigate the effect of pH gradients corresponding to levels typically found in the colon on GM composition and metabolite production using substrates inulin, lactose, galactooligosaccharides (GOS), and fructooligosaccharide (FOS) in an in vitro colon setup. We investigated 3 different pH regimes (low, 5.2 increasing to 6.4; medium, 5.6 increasing to 6.8 and high, 6.0 increasing to 7.2) for each fecal inoculum and found that colonic pH gradients significantly influenced in vitro simulated GM structure, but the influence of fecal donor and substrate was more pronounced. Low pH regimes strongly influenced GM with the decreased relative abundance of Bacteroides spp. and increased Bifidobacterium spp. Higher in vitro simulated colonic pH promoted the production of SCFAs in a donor- and substrate-dependent manner. The butyrate producer Butyricimonas was enriched at higher pH conditions, where also butyrate production was increased for inulin. The relative abundance of Phascolarctobacterium, Bacteroides, and Rikenellaceae also increased at higher colonic pH, which was accompanied by increased production of propionate with GOS and FOS as substrates.
CONCLUSIONS: Together, our results show that colonic substrates such as dietary fibres influence GM composition and metabolite production, not only by being selectively utilized by specific microbes, but also because of their SCFA production, which in turn also influences colonic pH and overall GM composition and activity. Our work provides details about the effect of the gradients of rising pH from the proximal to distal colon on fermenting dietary substrates in vitro and highlights the importance of considering pH in GM research.