Objective: To investigate the role of the biosynthetic gene cluster BGC3 of Streptococcus mutans (S. mutans) in the process of dental caries.
Methods: BGC3 and ∆BGC3 S. mutans strains were constructed and their growth curves were evaluated. Acid production capacity was assessed by evaluating pH reduction levels over identical culture periods. 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 qPCR. Co-culture experiments were conducted to evaluate bacterial adaptability. Bacterial viability was determined by microscopical examination of live/dead staining.
Results: Deletion of BGC3 did not significantly impact S. mutans growth or acid production in biofilms. The ∆BGC3 strain exhibited enhanced acid resistance and higher expression levels of virulence genes compared to the wild type. In addition, ∆BGC3 exhibited superior bacterial viability in the co-culture system.
Conclusion: BGC3 affected the acid resistance and expression of caries-related genes in S. mutans. The BGC3 knockout strain exhibited a more robust survival capability than the wild-type strain.
Keywords: biofilm, biosynthetic gene clusters, dental caries, Streptococcus mutans, virulence genes
