Molecular mechanisms involved in the acid tolerance response of Streptococcus mutans

grantor: University of TorontoThe acid tolerance response (ATR) plays a major role in the acid adaptation process in 'Streptococcus mutans'. The ATR is an inducible molecular response mechanism activated when the bacterium encounters a moderate pH that enables the cells to tolerate further drops in pH. Differential display PCR (dd-PCR) was used to identify and clone genes that were activated when 'S. mutans' was exposed to moderate pH (5.0). One of the dd-PCR products had 67% identity to a 'uvrA'/UV repair excinuclease gene in 'Bacillus subtilus. UvrA' knockouts were constructed in 'S. mutans' by PCR-mediated mutagenesis and were shown to be sensitive to UV irradiation and pH (5.0) when compared to the wild-type. Acid-adapted 'S. mutans uvrA' mutants were more resistant to UV irradiation than unadapted cells, but were unable to survive exposure to a killing pH of 3.0. Here we suggest that 'uvrA ' is necessary for the repair of acid-induced DNA damage and is essential for the ATR in 'S. mutans'.M.Sc