Biological characterisation of White-Line Inducing Principle (WLIP) produced by Pseudomonas reactans NCPPB1311

The biol. activities of the lipodepsipeptides (LDP) white line-inducing principle (WLIP), produced by Pseudomonas reactans NCPPB1311, and tolaasin I, produced by P. tolaasii NCPPB2192, were compared. Antimicrobial assays showed that both LDP inhibited the growth of fungi-including the cultivated mushrooms Agaricus bisporus, Lentinus edodes, and Pleurotus spp.-chromista, and gram-pos. bacteria. Assays of the two LDP on blocks of Agaricus bisporus showed their capacity to alter the mushrooms' pseudo-tissues though WLIP was less active than that of tolaasin I. Contrary to previous studies, tolaasin I was found to inhibit the growth of gram-neg. bacteria belonging to the genera Escherichia, Erwinia, Agrobacterium, Pseudomonas, and Xanthomonas. The only gram-neg. bacterium affected by WLIP was Erwinia carotovora subsp. carotovora. Both WLIP and tolaasin I caused red blood cell lysis through a colloid-osmotic shock mediated by transmembrane pores; however, the hemolytic activity of WLIP was greater than that of tolaasin I. Transmembrane pores, at a concn. corresponding to 1.5  C50, showed a radius between 1.5 and 1.70.1 nm for WLIP and 2.10.1 nm for tolaasin I. The antifungal activity of WLIP together with the finding that avirulent morphol. variants of P. reactans lack WLIP prodn. suggests that WLIP may play an important role in the interaction of the producing bacterium P. reactans and cultivated mushrooms.