Streptococcus mutans cause tooth decay via two mechanisms:

1. They produce a sticky, extracellular, dextran-based polysaccharide that allows them to stick to each other and tooth surfaces.

2. They produce lactic acid from various sugars including glucose, fructose, lactose which lowers the pH at the tooth surface and causes demineralization of tooth enamel (tooth decay).

If MAP and Streptococcus mutans function in a similar way, it would not be surprising to find similar virulence genes in the genomes of both organisms.

A study conducted by Tizard M et al, found genes that “encode functions related to LPS or extracellular polysaccharide biosynthesis” in the MAP genome: http://www.ncbi.nlm.nih.gov/pubmed/9884234

Similar functions exist in Streptococcus mutans: “Extracellular polysaccharides (PS) synthesized by oral bacteria [Streptococcus mutans] constitute one of their major virulence factors. The PS, synthesized from sucrose, facilitate adhesion and colonization by bacteria to tooth surfaces”: http://www.aobjournal.com/article/S0003-9969%2899%2900014-X/abstract#sec5