recA-dependence of the response of Pseudomonas aeruginosa to UVA and UVB irradiation.

The responses of the autochthonous soil and aquatic organism, Pseudomonas aeruginosa to UV radiation wavelengths (UVA, 320-400 nm, and UVB, 280-320 nm) has been investigated in this study. P. aeruginosa recA mutants were found to be more sensitive to both UVA and UVB radiation than were their isogenic RecA+ parents. Introduction of a low-copy-number plasmid containing the cloned wild-type P. aeruginosa recA gene restored UVA and UVB resistance to recA mutants. The concentration of RecA protein increased twofold 120 min after exposure to either UVA or UVB radiation, suggesting induction of expression of the recA gene by these wavelengths. In this study, we found that a functional RecA protein is required for activation of D3 prophage in lysogenic cells following exposure to UVB radiation. Prophage were not induced by exposure of their hosts to UVA radiation. Induction of damage-inducible (din) genes in response to UVA or UVB irradiation was also shown to be RecA dependent. These data indicate that the recA gene plays a role in the response of P. aeruginosa to exposure to wavelengths of UV radiation found in the solar spectrum.