FIG. 4.
Effects of overexpression of SOD and catalase on the survival of rpoS-deficient P. putida cells under carbon starvation conditions and on the frequency of accumulation of base substitution mutations. (A) Viability of the P. putida rpoS-deficient strain overexpressing catalase (rpoStackatA), SodAB (rpoStacsodAB), or both catalase and SodAB (rpoStackatAsodAB) on phenol minimal plates. The viability of the WT strain and its rpoS-deficient derivative without SOD or catalase overexpression is shown as well. (B) Accumulation of Phe+ revertants on phenol minimal plates in starving populations of the same strains shown in panel A. All strains carried the tester plasmid pKTpheA22TAG. Data for at least five parallel experiments are presented. In all cases, means ± standard deviations (error bars) for 10 plates calculated per 1 × 109 cells are shown.