Streptococcus mutans

Streptococcus mutans is a major etiological agent of human dental caries. Similar to other streptococci, the cell wall of S. mutans is composed of multiple layers of peptidoglycan decorated with glycopolymers that are characterized by the presence of l-rhamnose. Based on differences in the glycopolymer structures S. mutans is classified into four serotypes — cef and k. The serotype c-specific carbohydrate (SCC) of S. mutans is composed of a polyrhamnose backbone with α-linked glucose (Glc) side-chains. We have demonstrated that GroP modification is attached to the Glc side-chains of SCC and its spatially regulates cell division in S. mutans. We have showed that structurally-diverse SCCs display a specific distribution on the S. mutans cell surface with cell equators and poles being populated by ‘immature SCCs’, which are deficient in the GroP modification. These immature SCCs inform the proper positioning of the major cell separation autolysin AtlA and FtsZ through its cell wall binding regulator MapZ. Thus, the presence of GroP-modified SCC in the streptococcal cell wall provides an exclusion strategy for critical cell division proteins involved in the first and the final stages of streptococcal cell division. We aim to elucidate the cell wall structure targeted by MapZ and the mechanism of SCC assembly during different stages of S. mutans cell division. Work is underway to determine the function of glycerol phosphate modification in virulence properties of S. mutans.

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