Chromosomal Deletions in Streptococcus mutans

Abstract

The oral bacterium Streptococcus mutans possesses the ability to ferment a wide range of carbohydrates, which results in the production of acids that can cause demineralisation of tooth enamel and subsequent dental caries. However, it has been shown that approximately 11% of independent isolates of S. mutans from around the world lack the ability to ferment melibiose, raffinose, and on occasion β-glucosides (1,4). This is due to a deletion which extends through a region of the genome that includes the multiple sugar metabolism (msm) operon involved in the uptake and metabolism of a number of sugars (3). The msm region has been reintroduced to the deletion mutants by transformation and the ability to grow on galactose and β-glucosides was also restored, showing the linkage of the respective genes. The extent of the deletion is further being investigated with the use of pulsed field gel electrophoresis and Southern hybridizations with known S. mutans genes as probes.