Acyl homoserine lactone production by bacteria associated with cultivated mushrooms

The main bacterial pathogens of cultivated mushroom as well as mushroom-associated bacteria, which were isolated 9 from Agaricus bisporus, Pleurotus ostreatus, and Pleurotus eryngii mushroom niches, were evaluated for the production of N-acyl-L-10 homoserine lactones (AHLs) by using four bioreporters. Furthermore, identification of AHLs by LC-ESI-FTICR MS was performed on culture filtrates of selected pathogens and mushroom-associated bacteria strains, which resulted in inducing at least one of the four bioreporters. Strains of Burkolderia gladioli pv agariciola, Pseudomonas agarici, and Pseudomonas gingeri, but not those of Pseudomonas tolaasii and Pseudomonas reactans, produced an array of AHLs depending on the strain. This is the first report of AHL production by mushroom bacterial pathogens. Forty-four of 236 bacterial isolates obtained from different niches of cultivated mushrooms, in part identified by the Biolog identification system, were demonstrated to produce AHLs. Among them, seven mushroom-associated bacterial species were for the first time demonstrated to produce the above signal molecules. In the culture filtrates of a certain number of isolates/strains the AHL-hydrolyzed forms were also present. The minimal signal inducing concentration (MSIC) of selected pure AHLs was also determined for the four bioreporters used in this study.