The rpoS gene in Pseudomonas syringae is important in surviving exposure to the near-UV in sunlight

The near-UV component of sunlight decreased culturability of the leaf epiphyte and plant pathogen Pseudomonas syringae. Exposure of the wild-type cells for 4 h to UV-A and UV-B in sunlight was ten fold more detrimental than exposure to sunlight with just UV-A. Sensitivity to UV-A especially increased in a mutant of P. syringae lacking the global regulatory sigma factor, RpoS. No RpoS-mutant cells were culturable after 4 h of exposure to near-UV sunlight. These findings suggest that both UV-A and UV-B wavelengths cause damage to the bacterial cell and that the RpoS protein regulates protective measures for the leaf-associated pseudomonad.