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.
Highlights
Streptococcus mutans is an oral bacterium that is importantly involved in the development of dental caries and is a principal inducer of the oral biofilm formation containing various bacteria on the tooth surface [1,2,3,4]
To observe the effects of the initial pH on the formation of membrane vesicles (MVs) from S. mutans, media using a BHI broth were separately prepared at pH 6.0 by HC, lactic acid (LA), and acetic acid (AA)
The alkaline medium was prepared at pH 8.0 by NO
Summary
Streptococcus mutans is an oral bacterium that is importantly involved in the development of dental caries and is a principal inducer of the oral biofilm formation containing various bacteria on the tooth surface [1,2,3,4]. S. mutans is capable of releasing three types of glucosyltransferases (Gtfs, i.e., GtfB, GtfC, and GtfD) and synthesizing water-insoluble glucan and water-soluble glucan from sucrose by GtfB and GtfC to form a sticky oral biofilm [1,2,4,5]. The aggregation of bacterial cells using water-insoluble glucan synthesized by GtfB and the adhesion of bacteria using water-soluble and water-insoluble glucan synthesized by GtfC on the tooth surface are important aspects for the formation of biofilms, including other bacteria [4,5].
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