Changes to environmental pH alters the colon microbial community in terms of both structure and function: An in vitro analysis

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

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/14/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: A combination of physiology and microbial metabolism produces a pH gradient longitudinally through the colon, which is a critical factor for 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 in vitro. First, multiple donors were screened to elucidate a donor-independent response of the gut microbiota to environmental pH. Both raising and lowering the pH elicited structural and biochemical changes. Notably, when the pH was raised there was an increase in relative abundance of Firmicutes Clostridium and decrease in Proteobacteria Enterobacteriaceae with a corresponding increase in levels of short chain fatty acids (SCFAs). When the pH was lowered there was an increase in multiple taxa from Firmicutes and decrease in Bacteroidetes Alistipes, Proteobacteria Enterobacteriaceae, and Fusobacteria Fusobacterium corresponding to a decrease in total SCFAs. Next, a multicompartment model containing an ascending (AC), transverse (TC) and descending (DC) colon was used to determine the effect of pH on region specific communities. Raising the pH led to an increase in the abundance of Firmicutes Psuedoramibacter in the AC and an increase in Fusobacterium Fusobacteria and decrease in Firmicutes Megasphaera for all three compartments. Biochemically, these changes corresponded to a decrease in total SCFA levels for the DC, and a decrease in butyric, pentanoic, and total branched-chain SCFAs in all compartments. Lowering the pH decreased the abundance of Bacteroidetes Bacteroides and Parabacteroides and increased Firmicutes Dialaster and Proteobacteria Enterobacteriaceae in the AC, while decreasing the levels of Firmicutes Oscillospira and Fusobacteria Fusobacterium in the TC and DC. These changes corresponded to a drop in total SCFAs, acetic acid, and total branched-chain SCFA levels for all three colon regions. Taken together, these results indicate that environmental 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.