Effects of pH on the Properties of Membrane Vesicles Including Glucosyltransferase in Streptococcus mutans

Abstract

Streptococcus mutans releases membrane vesicles (MVs) and induces MV-dependent biofilm formation. Glucosyltransferases (Gtfs) are bound to MVs and contribute to the adhesion and glucans-dependent biofilm formation of early adherent bacteria on the tooth surface. The biofilm formation of S. mutans may be controlled depending on whether the initial pH tends to be acidic or alkaline. In this study, the characteristics and effects of MVs extracted from various conditions {(initial pH 6.0 and 8.0 media prepared with lactic acid (LA) and acetic acid (AA), and with NaOH (NO), respectively)} on the biofilm formation of S. mutans and early adherent bacteria were investigated. The quantitative changes in glucans between primary pH 6.0 and 8.0 conditions were observed, associated with different activities affecting MV-dependent biofilm formation. The decreased amount of Gtfs on MVs under the initial pH 6.0 conditions strongly guided low levels of MV-dependent biofilm formation. However, in the initial pH 6.0 and 8.0 solutions prepared with AA and NO, the MVs in the biofilm appeared to be formed by the expression of glucans and/or extracellular DNA. These results suggest that the environmental pH conditions established by acid and alkaline factors determine the differences in the local pathogenic activities of biofilm development in the oral cavity.

The effect of altered pH growth conditions on the production, composition, and proteomes of Helicobacter pylori outer membrane vesicles

“…In comparison, OMVs produced during acidic growth conditions were enriched in HomA and GmhA that contribute to bacterial adhesion to host epithelial cells [42, 43], and TlpC that has a role in bacterial chemotaxis [44], suggesting that proteins packaged in OMVs produced during acidic growth conditions may contribute to the initial chemotaxis, adhesion and colonization of H. pylori in the gastric mucosa. This finding is supported by earlier studies showing that environmental stress such as pH and bile salts can also change the composition of MVs produced by S. mutans, Vibrio fischeri and Campylobacter jejuni which subsequently altered their biological functions [36, 59–61]. Collectively, these findings indicate that pH growth conditions regulate the packaging of protein within BMVs which may also subsequently affect their biological functions within the host.…”

“…This finding is supported by earlier studies showing that environmental stress such as pH and bile salts can also change the composition of MVs produced by S. mutans, Vibrio fischeri and Campylobacter jejuni which subsequently altered their biological functions[36,[59][60][61]. Collectively, these findings indicate that pH growth conditions regulate the packaging of protein within BMVs which may also subsequently affect their biological functions within the host.Overall, this study highlights the significance of pH on H. pylori growth and their proteomes, and on the production, composition, and proteome of their OMVs.…”

Roles of bacterial extracellular vesicles in systemic diseases

“…MVs also promote the cariogenic ability of bacteria even at low pH values. Intriguingly, the initial pH value affects various characteristics of S. mutans MVs, including biofilm quantity ( Nakamura et al, 2020 ; Iwabuchi et al, 2021 ). Under low pH conditions, S. mutans released more MVs to deliver proteins related to cariogenesis, and several important enzymes carried by MVs, such as the shock heat proteins, lactate dehydrogenase, DexA and Gtfs, still possessed enzyme activity ( Cao et al, 2020 ).…”

Aspects of oral streptococcal metabolic diversity: Imagining the landscape beneath the fog

“…Notably, GtfB of S. mutans has been observed to bind to the exterior of other biofilm member species, essentially converting them to insoluble glucan producers. Membrane vesicles (MV) have been implicated in delivery of S. mutans Gtfs to the biofilm extracellular matrix (Iwabuchi et al, 2021;Senpuku et al, 2019). The effects of MV on commensal Streptococcal biofilm occupants are controversial, as both antagonistic and beneficial effects on commensal Streptococcal biofilm formation have been reported (Wu et al, 2022).…”