The impact of environmental pH on the gut microbiota community structure and short chain fatty acid production

Authors: Firrman, Jenni; Liu, Linshu; Mahalak, Karley; TU, VINCENT - Children'S Hospital - Philadelphia, Pennsylvania; TANES, CEYLAN - Children'S Hospital - Philadelphia, Pennsylvania; BITTINGER, KYLE - Children'S Hospital - Philadelphia, Pennsylvania; BOBOKALONOV, JAMSHED - US Department Of Agriculture (USDA); MATTEI, LISA - Children'S Hospital - Philadelphia, Pennsylvania; ZHANG, HUANJIA - Children'S Hospital - Philadelphia, Pennsylvania; VAN DEN ABEELE, PIETER - Prodigest

Submitted to: FEMS Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2022
Publication Date: 4/6/2022
Citation: Firrman, J., Liu, L.S., Mahalak, K.K., Tu, V., Tanes, C., Bittinger, K., Bobokalonov, J., Mattei, L., Zhang, H., Van Den Abeele, P. 2022. The impact of environmental pH on the gut microbiota community structure and short chain fatty acid production. FEMS Microbiology Ecology. 98(5). https://doi.org/10.1093/femsec/fiac038.
DOI: https://doi.org/10.1093/femsec/fiac038

Interpretive Summary: The gut microbiota is a dense community of microbes that lives in the human colon and is important to human health. The type of microbes and the short chain fatty acids they release, small compounds produced by the microbes, depends on the environment within the colon, which is affected by pH (a measure of acidity or alkalinity). It is known that the individual microbes are affected by pH levels, with some of the microbes growing only under particular pH conditions. However, the effect of pH on the gut microbiota as a community was unclear. Here, we tested how the gut microbiota responded to raising and lowering the environmental pH. We found that the abundance of some microbes either increased or decreased depending on pH. The short chain fatty acids that the community released were also affected by changes to environmental pH. In conclusion, this study demonstrated that the environmental conditions of the colon, such as pH, will impact the gut microbiota and can cause changes to the community, which may play a role in human health and disease prevention.

Technical Abstract: A combination of physiology and microbial metabolism produces a pH gradient longitudinally through the colon, which is a critical factor for the development of the gut microbial community. Here, the response of the gut microbiota to incremental alterations of pH was evaluated to explicate the role of pH on community structure and biochemical function. This was accomplished using in vitro methods to first, evaluate the effect of pH change on communities established from multiple donors and second, to decipher how pH influences communities that develop within the distinct biogeographical colon regions. The results found that the effect of pH change on alpha diversity was donor dependent. However, significant changes in relative abundance of families such as Erysipelotrichaceae, Desulfovibrionaceae, Veillonellaceae, Fusobacteriaceae, and Lachnospiraceae, and biochemically, changes in levels of short chain fatty acids (SCFAs) were observed in a donor-independent manner. Region specifically, the ascending colon community exhibited the most prominent pH-dependent change in alpha diversity and overall shift in community structure. There were a number of region-dependent changes in relative abundance of families observed yet shifts in Veillonellaceae and Fusobacteriaceae occurred in all colon regions. Biochemically, SCFA levels significantly changed in response to pH, with the most apparent changes observed in the AC region. Taken together, these results indicate that pH is an important contributor to community homeostasis, and alterations to this environmental condition can modulate the gut microbiota community structure and function, which plays an important role in human health and disease prevention.