Biofilm formation on glycated collagen modulates Streptococcus mutans bacterial extracellular vesicle production and cargo

Streptococcus mutans is the major microbial etiological agent of dental caries and can adhere to surfaces such as type-I collagen, present in dentin and periodontal tissues. Recent studies have characterized planktonic S. mutans bacterial extracellular vesicles (bEVs) and demonstrated environmental-induced changes due to sugar presence or pH alterations. However, to date there are no studies exploring if surface-derived changes - such as tissue glycation - can modulate bEV production in the context of oral biofilm formation in the elderly. Therefore, the aim of this work was to determine the role of biofilm formation and collagen glycation on the morphology and composition of S. mutans bEVs. For this, bEVs from S. mutans biofilms on native and glycated collagen surfaces were isolated, characterized, and compared to bEVs from planktonic cells. Nanoparticle tracking analysis and microscopy confirmed bEV production and showed that bEVs from biofilms are smaller in size and less abundant than those from planktonic cells. Furthermore, proteome analysis revealed that S. mutans biofilm formation on native and glycated collagen led to the enrichment of several key virulence proteins such as Eno, LuxS, Tpx, and ScrB. Also, a shift towards proteins involved in metabolic processes was found in bEVs following biofilm formation on collagen surfaces, whereas glucan metabolism proteins were overexpressed in vesicles from the planktonic state. These results demonstrate that biofilm formation, as well as the glycation of collagen associated with aging and hyperglycemia, can modulate bEV characteristics and cargo and could play a central role in S. mutans virulence and the development of diseases such as dental caries and periodontal disease.