[Latest Findings on Polyketides/Non-ribosomal Peptides That Are Secondary Metabolites of Streptococcus mutans]

[Research Progress on Drug Intervention to Inhibit Dental Plaque Biofilm Formation by Streptococcus mutans Based on the Concept of Ecological Prevention of Dental Caries]

Dental caries is the local destruction of hard tooth tissue caused by acidic byproducts generated by cariogenic bacteria, primarily Streptococcus mutans, which ferment free sugars in the presence of host factors, dietary components, and environmental conditions. A main feature of dental caries is the formation of dental plaque biofilm, which significantly improves the resistance of bacteria to drugs and host immunity. Traditional anti-caries drugs mainly exert anti-biofilm functions indirectly through antibacterial activities. However, they tend to interfere with the symbiotic microbiota while inhibiting cariogenic bacteria, which may cause imbalance within the oral microbial system. With increasing attention paid to the homeostasis of oral microbiota, new types of anti-caries drugs have been developed, such as natural extracts, artificially synthesized small molecules, and oligonucleotides. They act on key targets to inhibit the formation of biofilm substrates or regulate the interactions between oral microorganisms, thereby efficiently inhibiting biofilm formation. These drugs do not have bactericidal effects. Nevertheless, they exert indirect antimicrobial effects by interfering with biofilm substrate formation or microbial interactions. The optimization of delivery carriers, combination drug therapy, and biomimetic design further enhance the efficacy of these new types of anti-caries drugs. This article provides a review of the prevention and treatment principles and key targets of dental plaque biofilm. We also discussed the types, mechanisms of action, and development trends of relevant drugs.

Polyketides/nonribosomal peptides from Streptococcus mutans and their ecological roles in dental biofilm

Streptococcus mutans is the major etiological agent of dental caries in humans. S. mutans overgrowth within dental biofilms can trigger biofilm dysbiosis, ultimately leading to the initiation or progression of dental caries. Polyketides and nonribosomal peptides (PKs/NRPs) are secondary metabolites with complex structures encoded by a cluster of biosynthetic genes. Although not essential for microbial growth, PKs/NRPs play important roles in physiological regulation. Three main classes of hybrid PKs/NRPs in S. mutans have been identified, including mutanobactin, mutanocyclin, and mutanofactin, encoded by the mub, muc, and muf gene clusters, respectively. These three hybrid PKs/NRPs play important roles in environmental adaptation, biofilm formation, and interspecies competition of S. mutans. In this review, we provide an overview of the major hybrid PKs/NRPs of S. mutans, including mutanobactin, mutanocyclin, and mutanofactin and address their ecological roles in dental biofilms. We place specific emphasis on important questions that are yet to be answered to provide novel insights into the cariogenic mechanism of S. mutans and facilitate improved management of dental caries. We highlight that S. mutans PKs/NRPs may be potential novel targets for the prevention and treatment of S. mutans-induced dental caries. The development of genomics, metabolomics, and mass spectrometry, together with the integration of various databases and bioinformatics tools, will allow the identification and synthesis of other secondary metabolites. Elucidating their physicochemical properties and their ecological roles in oral biofilms is crucial in the identification of novel targets for the ecological management of dental caries.