ppGpp accumulation in Pseudomonas aeruginosa and Pseudomonas fluorescens subjected to nutrient limitation and biocide exposure

The effect of a commonly used biocide, 1,2- benzisothiazolin-3-one (BIT) on ppGpp accumulation in the pathogen, Pseudomonas aeruginosa PAO1, and an en vironmental isolate, Ps. fluorescens, was examined. It is concluded that BI T is able to induce a stringent response in Ps. aeruginosa and Ps. fluoresc ens, determined by the rapid accumulation of ppGpp following addition of BI T to exponentially-growing cells. Western blot analysis of whole-cell extra cts with anti-RelA antibody demonstrated that both species contain a RelA h omologue. This is the first report of a RelA-like protein in pseudomonads.