Host Components and a Complex Bacterial Sensor Kinase, RtpA, Determine the Pathogenic Process of Pseudomonas tolaasii on a Cultivated Mushroom, Pleurotus ostreatus

Abstract

Pseudomonas tolaasii, the pathogen of brown blotch disease in a cultivated mushroom, Pleurotus ostreatus, produces extracellular toxins (tolaasins) that are the major cause of symptoms. Components of the fruiting bodies activate tolaasin production and suppress the occurrence of avirulent variants of the bacterium. Single mini-Tn5km1 insertions in P. tolaasii strain PT814 yielded mutants that are avirulent to P. ostreatus but weakly virulent to Agaricus bisporus, causing yellow blotch rather than typical brown blotch. Mutants are pleiotropically deficient in tolaasin as well as protease production, but sustain a normal level of volatile toxin (tovsin) in vitro. These characteristics resemble variants from a genetically unstable P. tolaasii strain, S8501. The rtpA gene required for tolaasin production in the pleiotropic mutants was cloned. Nucleotide sequence predicted that RtpA has a striking homology to the BvgS family of bacterial two-component regulators. Observations suggest that signals from hosts stimulate the production of factors important to virulence of P. tolaasii.KeywordsProtease ProductionStationary Growth PhasePleurotus OstreatusBordetella PertussisAgaricus BisporusThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.