Exploring the impact of biosynthetic gene cluster BGC3 on the cariogenic virulence of Streptococcus mutans

Abstract

Abstract This study focused on the biosynthetic gene cluster BGC3 of Streptococcus mutans, a primary pathogen in dental caries, and its effects on the cariogenic virulence of Streptococcus mutans. BGC3 and ∆BGC3 Streptococcus mutans strains were constructed, and their growth curves were evaluated. Further, their acid production capacity was assessed by comparing their pH reduction levels. The survival of bacteria in phosphate citrate buffer solution (pH 3.0) was quantified. The expression levels of virulence genes (atpF, gtfC, gtfD, spaP, vicR, and ftf) were analysed using the reverse transcription-quantitative polymerase chain reaction. Bacterial viability was determined by microscopical examination of live/dead staining. Co-culture experiments were conducted to evaluate bacterial adaptability. The elimination of BGC3 did not significantly impact Streptococcus mutans growth or acid production in biofilms. The ∆BGC3 strain exhibited enhanced acid resistance and higher expression levels of virulence genes. In co-culture, ∆BGC3 exhibited superior bacterial viability. BGC3 reduced the cariogenic virulence of Streptococcus mutans in terms of acid tolerance and the expression of related genes. The knockout strain exhibited a more robust survival capability than the wild-type strain.