Differential roles of the Pseudomonas aeruginosa PA14 rpoN gene in pathogenicity in plants, nematodes, insects, and mice

We cloned the rpoN (ntrA, glnF) gene encoding the alternate sigma factor si gma (54) from the opportunistic multihost pathogen Pseudomonas aeruginosa s train PA14. A marker exchange protocol was used to construct the PA14 rpoN insertional mutation rpoN::Gen(r) PA14 rpoN::Gen(r) synthesized reduced lev els of pyocyanin and displayed a variety of phenotypes typical of rpoN muta nts, including a lack of motility and the failure to grow on nitrate, gluta mate, or histidine as the sole nitrogen source. Compared to wild-type PA14, rpoN::Gen(r) was ca. 100-fold less virulent in a mouse thermal injury mode l and was significantly impaired in its ability to kill the nematode Caenor habditis elegans. In an Arabidopsis thaliana leaf infectivity assay, althou gh rpoN::Gen(r) exhibited significantly reduced attachment to trichomes, st omata, and the epidermal cell surface, did not attach perpendicularly to or perforate mesophyll cell walls, and proliferated less rapidly in Arabidops is, leaves, it nevertheless elicited similar disease symptoms to wild-type P. aeruginosa PA14 at later stages of infection. rpoN.:Gen was not impaired in virulence in a Galleria mellonella (greater wax moth) pathogenicity mod el. These data indicate that rpoN does not regulate the expression of any g enes that encode virulence factors universally required for P. aeruginosa p athogenicity in diverse hosts.