Production of Tolaasin I and WLIP by Pseudomonas tolaasii and P. “reactans”, their Antimicrobial Activity and Possible Role in the Virulence of the Pathogens

Shaken culture in KB of strain NCPPB2192 of Pseudomonas tolaasii showed an activity of 3,200 and 800 units ml−1 toward Bacillus megaterium and Rhodotorula pilimanae, respectively. On the contrary, an activity of 400 units ml−1 toward B. megaterium was observed with the cultures of strain NCPPB1311 of P. “reactans”. The purification of lipodepsipeptides from the cultures of P. tolaasii and P. “reactans” yielded about 13 mg l−1 of tolaasin and 169 mg l−1 of White Line Inducing Principle (WLIP), respectively. Antimicrobial assays showed that HPLC grade tolaasin I inhibited the growth of filamentous fungi and yeasts and Gram positive bacteria. Only a limited activity was observed toward some Gram negative bacteria. Of particular interest is the activity of tolaasin I toward phytopathogenic fungi, Pleurotus and Agaricus spp., as well as yeasts and filamentous fungi responsible for mycoses of mammals. WLIP inhibited the growth of fungi and Gram positive bacteria, though at higher concentration when compared to tolaasin I, but not that of Gram negative bacteria. Assays of the two toxins on blocks of A. bisporus confirmed the antifungal activity of the two lipodepsipeptides and suggested their possible role in the symptoms caused by the mushroom bacterial pathogens.