Novel sucrose-dependent adhesion co-factors in Streptococcus mutans

Area of Science:

• Microbiology
• Oral Health
• Bacterial Adhesion

Background:

• Streptococcus mutans utilizes glucosyltransferases to synthesize extracellular glucans from sucrose, facilitating tooth adhesion.
• The precise mechanisms governing S. mutans sucrose-dependent adhesion are not fully understood, suggesting potential involvement of additional factors.

Purpose of the Study:

• To investigate novel factors beyond glucosyltransferases that influence Streptococcus mutans' adhesion to teeth in a sucrose-dependent manner.

Main Methods:

• Screening of a pVA891-insertion mutant library of S. mutans LT11 to identify mutants with impaired sucrose-dependent adhesion.
• Genetic identification of loci flanking insertion sites in adhesion-deficient mutants.
• Phenotypic analysis and in vivo colonization studies in a rat model.

Main Results:

• Four distinct genetic loci were identified in mutants showing reduced adhesion to glass in the presence of sucrose: glycerol-3-phosphate dehydrogenase, an ABC transporter, a multidrug-efflux pump, and either the ribulose monophosphate or ascorbate metabolism operon.
• The multidrug efflux pump mutant exhibited a complete failure in colonizing rat models.
• The other three mutants demonstrated colonization capabilities, suggesting potential reversion to wild-type or compensatory mechanisms.

Conclusions:

• Glycerol-3-phosphate dehydrogenase, an ABC transporter, a multidrug efflux pump, and genes involved in ribulose monophosphate or ascorbate metabolism are identified as potential contributors to Streptococcus mutans' sucrose-dependent adhesion.
• The multidrug efflux pump plays a critical role in the in vivo colonization of Streptococcus mutans.