|Whistler, C. - OREGON STATE UNIVERSITY|
|Sarniguet, A. - INRA, RENNES, FRANCE|
|Stockwell, V. - OREGON STATE UNIVERSITY|
Submitted to: International Congress on Pseudomonas Molecular Biology and Biotechnology
Publication Type: Proceedings
Publication Acceptance Date: June 1, 1997
Publication Date: N/A
Technical Abstract: Pseudomonas fluorescens Pf-5 is a rhizosphere bacterium that produces at least three antibiotics, including pyoluteorin, pyrrolnitrin, and 2,4-diacetylphoroglucinol, and suppresses seedling diseases caused by the soilborne fungi Rhizoctonia solani and Pythium ultimum. Three global regulatory genes are known to influence antibiotic production by Pf-5. apdA encodes a sensor kinase and gacA encodes a response regulator of a putative two component regulatory system; mutants with genetic lesions in either apdA or gacA produce none of the antibiotics. The stationary-phase sigma factor RpoS is a differential regulator of antibiotic biosynthesis genes; an RpoS- mutant overproduces pyoluteorin and 2,4-diacetylphloroglucinol and produces no pyrrolnitrin. ApdA-, GacA-, and RpoS- mutants were impaired in survival of oxidative stress compared to wildtype Pf-5. A study was initiated to determine the interactions of the three global regulators. At the entrance to stationary phase, ApdA, and GacA positively influenced both the accumulation of RpoS, assessed by western analysis, and the induction of rpoS transcription, assessed with a transcriptional fusion to the chromosomal rpoS of Pf-5. A fourth global regulator, a protease La homologue encoded by lon, negatively influenced pyoluteorin production but had no effect on the other two antibiotics produced by Pf-5. A Lon- mutant was less capable than wildtype Pf-5 of surviving UV damage. Our results indicate that protease La, ApdA, GacA, and RpoS comprise four global regulators that influence both antibiotic production and stress response of P. fluorescens.