Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, Tallinn, Estonia.
Center of Food and Fermentation Technologies, Akadeemia tee 15A, Tallinn, Estonia.
FEMS Microbiol Lett. 2021 May 4;368(7). doi: 10.1093/femsle/fnab042.
Environmental pH and gut transit rate are the key factors determining the dynamics of colonic microbiota. In this study, the effect of changing pH on the composition and metabolism of pooled faecal microbiota was elucidated at physiologically relevant dilution rates Dhigh = 0.2 and Dlow = 0.05 1/h. The results showed the best adaptability of Bacteroides ovatus within the pH range 6.0-8.0 at both dilution rates. The butyrate producing Faecalibacterium and Coprococcus comes were extremely sensitive to pH > 7.5, while the abundance of Akkermansia muciniphila increased significantly at pH >7 at Dhigh, causing a pH-dependant shift in the dynamics of mucin degrading species. Increased gas formation was observed at pH < 6.5. Substantially more CO2 was produced at Dlow than at Dhigh (18-29 vs 12-23 mmol per L medium, respectively). Methane was produced only at Dlow and pH > 7, consistent with the simultaneous increased abundance of Methanobrevibacter smithii. Our study confirmed the importance of pH in the development of faecal microbiota in pectin-supplemented medium. Fermentation of other dietary fibres can be studied using the same approach. The significance of pH should be more emphasized in gut research and diagnostics.
环境 pH 值和肠道转运速率是决定结肠微生物区系动态变化的关键因素。在这项研究中，以生理相关的稀释率 Dhigh=0.2 和 Dlow=0.05 1/h 阐明了改变 pH 值对 pooled 粪便微生物群组成和代谢的影响。结果表明，在两种稀释率下，Bacteroides ovatus 在 pH 值 6.0-8.0 范围内具有最佳的适应性。产丁酸的 Faecalibacterium 和 Coprococcus 对 pH 值>7.5 极其敏感，而 Akkermansia muciniphila 的丰度在 Dhigh 时 pH 值>7 时显著增加，导致粘蛋白降解物种的动态发生 pH 依赖性变化。在 pH 值<6.5 时观察到气体形成增加。与 Dhigh 相比，Dlow 时产生的 CO2 显著更多（分别为 18-29 mmol/L 培养基和 12-23 mmol/L 培养基）。仅在 Dlow 和 pH 值>7 时产生甲烷，这与 Methanobrevibacter smithii 的同时丰度增加一致。我们的研究证实了 pH 值在果胶补充培养基中粪便微生物群发育中的重要性。可以使用相同的方法研究其他膳食纤维的发酵。在肠道研究和诊断中，应该更加重视 pH 值的重要性。
