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 environmental isolate, Ps. fluorescens, was examined. It is concluded that BIT is able to induce a stringent response in Ps. aeruginosa and Ps. fluorescens, determined by the rapid accumulation of ppGpp following addition of BIT to exponentially‐growing cells. Western blot analysis of whole‐cell extracts with anti‐RelA antibody demonstrated that both species contain a RelA homologue. This is the first report of a RelA‐like protein in pseudomonads.