1Dipartimento di Biologia, Difesa e Biotecnologie Agro Forestali, Università degli Studi della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy; 2Dipartimento di Scienze del Suolo, della Pianta e dell'Ambiente, Università di Napoli “Federico II”, Portici (Napoli), Italy; 3CNR-ITC Istituto di Biofisica-Sezione di Trento, Povo (Trento); 4Dipartimento di Sanità e Benessere Animale, Università di Bari, Italy
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Accepted 8 June 2006.
The biological activities of the lipodepsipeptides (LDP) white line-inducing principle (WLIP), produced by Pseudomonas reactansNCPPB1311, 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-positive 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-negative bacteria belonging to the genera Escherichia, Erwinia, Agrobacterium, Pseudomonas, and Xanthomonas. The only gram-negative 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 haemolytic activity of WLIP was greater than that of tolaasin I. Transmembrane pores, at a concentration 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 morphological variants of P. reactans lack WLIP production suggests that WLIP may play an important role in the interaction of the producing bacterium P. reactans and cultivated mushrooms.
© 2006 The American Phytopathological Society