Fig. 2.

The results of qRT-PCR experiments reveal increased transcription of the S. mutans sod, tpx, and sloC genes in the SloR-deficient GMS584 strain compared to the UA159 wild-type SloR-proficient progenitor strain UA159 under conditions of oxidative stress. Gene expression was normalized against that of an endogenous hk11 control gene. Expression deriving from continuously aerated S. mutans cultures was normalized against that of control cultures of the same strain to allow for expression comparisons between UA159 and GMS584 (N = 3 independent experiments, with each expression level measured in triplicate). An independent samples t-test revealed significant up-regulation of sod gene expression in GMS584 compared to UA159 under conditions of continuous aeration compared to controls (p = 0.050, df = 4). Expression trends for tpx and sloC were similar and remarkable in a Cohen’s d test, demonstrating increased transcription in the SloR-deficient mutant compared to the SloR-proficient wild-type progenitor. Error bars represent the standard error of the mean (SEM) for normalized gene expression.