Here, we studied the role of PolIV, ImuB and DnaE2 in
Pseudomonas aeruginosa (PA) stress-induced mutagenesis. We
constructed PAO1 dinB, imuB and dnaE2 mutants and analyzed
their role in UV-induced mutagenesis. After UV irradiation, PAO1
showed a 2.6 fold increase (P=0.038) in the mutation frequency
confirming that PA displays a subtle UV-induced mutator
phenotype. PolIV deficiency resulted in levels of UV-induced
mutagenesis similar to the wild type strain (ratio 3.6; P=0.019). In
contrast, imuB (ratio 0.83, P=0.09) and dnaE2 (ratio 0.72, P=0.2)
showed no increase in the mutation frequencies after induction,
indicating that UV-induced mutagenesis in PA might depend on
ImuB and DnaE2 but not on PolIV. We further investigated the role
of these DNA polymerases in stationary-phase mutagenesis using a
plasmid-based test system that allows the detection of -1 deletions
and substitutions. These plasmids contain the reporter gene pheA
harboring loss-of-function mutations that produce phenol
monooxygenase inactivation, but whose reversion allows bacteria
to grow using phenol as the sole carbon source. Results obtained
from the incubation of PAO1 carrying the plasmids on phenol
selective plates showed that PA displays stationary-phase
mutagenesis. We are currently analyizing dinB, imuB and dnaE2
strains in order to study the role of these DNA polymerases in
stationary-phase mutagenesis.
