Vinay Gianni, Seppen Jurgen, Setlow Peter, Brul Stanley
Tytgat Institute for Liver and Intestinal Research, Amsterdam University Medical Centers, Location AMC, University of Amsterdam, Amsterdam 1105 AZ, The Netherlands.
Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030-3305, United States.
FEMS Microbiol Rev. 2025 Jan 14;49. doi: 10.1093/femsre/fuaf005.
Bacterial spores formed upon metabolic stress have minimal metabolic activity and can remain dormant for years. Nevertheless, they can sense the environment and germinate quickly upon exposure to various germinants. Germinated spores can then outgrow into vegetative cells. Germination of spores of some anaerobes, especially Clostridioides difficile, is triggered by cholic acid and taurocholic acid. Elevated levels of these bile acids are thought to correlate with a perturbed gut microbiome, which cannot efficiently convert primary bile acids into secondary bile acids. That bile acids are germination-triggers suggests these bacteria have a life cycle taking place partially in the mammalian digestive tract where bile acids are plentiful; notably bile acids can be made by all vertebrates. Thus, spores survive in the environment until taken up by a host where they encounter an environment suitable for germination and then proliferate in the largely anaerobic large intestine; some ultimately sporulate there, regenerating environmentally resistant spores in the C. difficile life cycle. This review summarizes current literature on the effects of bile acids and their metabolites on spore germination in the gut and evidence that adaptation to bile acids as germinants is a consequence of a life cycle both inside and outside the digestive tract.
在代谢应激下形成的细菌孢子代谢活性极低，可保持休眠数年。然而，它们能够感知环境，并在接触各种萌发剂后迅速萌发。萌发后的孢子随后可生长为营养细胞。某些厌氧菌，特别是艰难梭菌的孢子萌发，是由胆酸和牛磺胆酸触发的。这些胆汁酸水平的升高被认为与肠道微生物群紊乱有关，肠道微生物群无法有效地将初级胆汁酸转化为次级胆汁酸。胆汁酸作为萌发触发因素表明，这些细菌的生命周期部分发生在胆汁酸丰富的哺乳动物消化道中；值得注意的是，所有脊椎动物都能产生胆汁酸。因此，孢子在环境中存活，直到被宿主摄取，在那里它们遇到适合萌发的环境，然后在基本厌氧的大肠中增殖；有些最终在那里形成孢子，在艰难梭菌的生命周期中重新产生对环境有抗性的孢子。本综述总结了当前关于胆汁酸及其代谢产物对肠道孢子萌发影响的文献，以及适应胆汁酸作为萌发剂是消化道内外生命周期结果的证据。
