Biological Characterization of White Line-Inducing Principle (WLIP) Produced by Pseudomonas reactans NCPPB1311

Abstract

The biological activities of the lipodepsipeptides (LDP) white line-inducing principle (WLIP), produced by Pseudomonas reactans NCPPB1311, and tolaasin I, produced by R 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 x 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.

Pathogenic variation in isolates of Pseudomonas causing the brown blotch of cultivated mushroom, Agaricus bisporus

“…The two Pseudomonas isolates in group (II) which produced typical white line (Characteristic to P. "reactans") against P. tolaasii reference strain were identified as Pseudomonas spp. The inability to reach the species level for them analyzing their nutritional profile is attributed to a fact that P. "reactans" is still a non-classified bacterium in the data bank of the Biolog system and known to produces an extracellular substance called "WLIP" which plays a role in the interaction with cultivated mushrooms (16). The other two isolates with a weak WLA reaction against P. tolaasii, were identified as P. gingeri, Munsch and Alatossava (20) found that a strain of P. gingeri was able to produce a typical WLA when streaked towards a reference strain of P. tolaasii and they hypothesized that the bacterium produces some compounds behaving like the WLIP molecule and may be structurally identical or with similar biological function to the one produced by P. "reactans".…”

Structure and X-ray conformation of pseudodesmins A and B, two new cyclic lipodepsipeptides from Pseudomonas bacteria

“…Within the viscosin group this has been postulated for viscosinamide, which is believed to induce Ca 2+ transporting pores to inhibit fungal growth 13 . Furthermore, WLIP has been shown to insert itself within model membranes 20 , while its pore forming capability was demonstrated on erythrocytes using osmotic protectants 12 . The observed properties of pseudodesmin A are in agreement with such behaviour.…”

“…Full elucidation of the covalent structure was achieved through NMR, LC-MS and X-Ray diffraction analysis, revealing pseudodesmin A and B to be new members of the viscosin group. For certain viscosin group members, transmembrane pore formation has been proposed as the most likely biological mode of action 12,13 . Using the crystal structure of pseudodesmin A, potential links between the structure and this mode of action are discussed.…”

Cellular Responses of the Late Blight Pathogen Phytophthora infestans to Cyclic Lipopeptide Surfactants and Their Dependence on G Proteins

“…Blood cells (2 l) were mixed with PBS containing 50 mM of a sugar or polyethylene glycol to give a final volume of 1 ml and a final OD 600 of 0.3 to 0.4. The osmotic protectants used were glucose (0.42 nm), sucrose (0.54 nm), raffinose (0.66 nm), and polyethylene glycol with molecular weights of 1,000 (0.92 nm), 1,500 (1.2 nm), 3,350 (1.8 nm), and 4,000 (2.0 nm); the hydrodynamic radius of each osmolite in nm, taken from data reported previously by Lo Cantore et al (26), is shown in parentheses after each compound. The cells were incubated for 5 min at RT before the addition of purified Mass A to a final concentration of 5 g ml…”