Normalized sod mRNA expression levels. The relative expression ratios are the average values from 3 replicate cultures. Bars indicate the 95% confidence interval of the mean (non-overlapping intervals denote significant differences at the 0.05 level). This statistic is a conservative criterion of statistical significance. All sod expression levels were normalized using the geometric mean of cdc-42, pmp-3 and Y45F10D.4.