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One of the popular ideas is that decline in methyl-directed mismatch repair (MMR) in carbon-starved bacteria might facilitate occurrence of stationary-phase mutations. We compared the frequency of accumulation of stationary-phase mutations in carbon-starved Pseudomonas putida wild-type and MMR-defective strains and found that knockout of MMR system increased significantly emergence of base substitutions in starving P. putida. At the same time, the appearance of 1-bp deletion mutations was less affected by MMR in this bacterium. The spectrum of base substitution mutations which occurred in starving populations of P. putida wild-type strain was distinct from mutation spectrum identified in MMR-defective strains. The spectrum of base substitutions differed also in this case when mutants emerged in starved populations of MutS or MutL-defective strains were comparatively analyzed. Based on our results we …