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Tolaasin, a toxic secretion by Pseudomonas tolaasii , is the cause of bacterial brown blotch disease of edible mushrooms. [1] Tolaasin is composed of 18 amino acids, including a beta-hydroxy-octanoic acid chain located at the N terminus. [2] Tolaasin is a 1985 Da lipodepsipeptide non-host specific toxin. In addition to forming an amphipathic left handed alpha-helix in a hydrophobic environment, the toxin has been shown to form Zn2+-sensitive voltage-gated ion channels in planar lipid bilayers and to catalyze erythrocyte lysis by a colloid osmotic mechanism. [3] At high concentrations, tolaasin acts as a detergent that is able to directly dissolve eukaryotic membranes.[1] The fungal cell membranes are disrupted by the lipopeptides through the formation of trans-membrane pores. [2] Tolaasin pores disrupt the cellular osmotic pressure, leading to membrane collapse. Compounds that inhibit the toxicity of tolaasin have been identified from varying food additives. Tolaasin cytotoxicity can be effectively inhibited by food detergents, as well as sucrose and polyglycerol esters of fatty acids. [4]

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Edible mushrooms are the fleshy and edible fruit bodies of several species of macrofungi. Edibility may be defined by criteria including the absence of poisonous effects on humans and desirable taste and aroma. Edible mushrooms are consumed for their nutritional and culinary value. Mushrooms, especially dried shiitake, are sources of umami flavor.

<span class="mw-page-title-main">Exotoxin</span> Toxin from bacteria that destroys or disrupts cells

An exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell. Gram negative pathogens may secrete outer membrane vesicles containing lipopolysaccharide endotoxin and some virulence proteins in the bounding membrane along with some other toxins as intra-vesicular contents, thus adding a previously unforeseen dimension to the well-known eukaryote process of membrane vesicle trafficking, which is quite active at the host–pathogen interface.

<span class="mw-page-title-main">Polymyxin</span> Group of antibiotics

Polymyxins are antibiotics. Polymyxins B and E are used in the treatment of Gram-negative bacterial infections. They work mostly by breaking up the bacterial cell membrane. They are part of a broader class of molecules called nonribosomal peptides.

<span class="mw-page-title-main">Enterotoxin</span> Toxin from a microorganism affecting the intestines

An enterotoxin is a protein exotoxin released by a microorganism that targets the intestines. They can be chromosomally or plasmid encoded. They are heat labile (>60⁰), of low molecular weight and water-soluble. Enterotoxins are frequently cytotoxic and kill cells by altering the apical membrane permeability of the mucosal (epithelial) cells of the intestinal wall. They are mostly pore-forming toxins, secreted by bacteria, that assemble to form pores in cell membranes. This causes the cells to die.

<span class="mw-page-title-main">Anthrax toxin</span> Tripartite protein complex secreted by virulent strains of Bacillus anthracis

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Cytolysin refers to the substance secreted by microorganisms, plants or animals that is specifically toxic to individual cells, in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are named accordingly. For instance, the cytolysins responsible for the destruction of red blood cells, thereby liberating hemoglobins, are named hemolysins, and so on. Cytolysins may be involved in immunity as well as in venoms.

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Pseudomonas tolaasii is a species of Gram-negative soil bacteria that is the causal agent of bacterial blotch on cultivated mushrooms. It is known to produce a toxin, called tolaasin, which is responsible for the brown blotches associated with the disease. It also demonstrates hemolytic activity, causing lysis of erythrocytes. Based on 16S rRNA analysis, P. tolaasii has been placed in the P. fluorescens group.

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  1. Hutchison, M. L.; Johnstone, K. J. (1993). "Evidence for the involvement of the surface active properties of the extracellular toxin tolaasin in the manifestation of brown blotch disease symptoms by Pseudomonas tolaasii on Agaricus bisporus". Physiol. Molec. Pl. Pathol. 42 (6): 373–384. doi:10.1016/S0885-5765(05)80013-X.
  2. 1 2 Scherlach, Kirstin; Lackner, Gerald; Graupner, Katharina; Pidot, Sacha; Bretschneider, Tom; Hertweck, Christian (2013-12-16). "Biosynthesis and Mass Spectrometric Imaging of Tolaasin, the Virulence Factor of Brown Blotch Mushroom Disease". ChemBioChem. 14 (18): 2439–2443. doi:10.1002/cbic.201300553. ISSN   1439-4227. PMID   24222604. S2CID   43528692.
  3. Rainey, P. B.; Brodey, C. L.; Johnstone, K. J. (1991). "Biological properties and spectrum of activity of tolaasin, a lipodepsipeptide toxin produced by the mushroom pathogen Pseudomonas tolaasii. on Agaricus bisporus". Physiol. Molec. Pl. Pathol. 39 (1): 57–70. doi:10.1016/0885-5765(91)90031-C.
  4. Yun, Yeong-Bae; Cho, Kwang-Hyun; Kim, Young-Kee (January 2023). "Inhibition of Tolaasin Cytotoxicity Causing Brown Blotch Disease in Cultivated Mushrooms Using Tolaasin Inhibitory Factors". Toxins. 15 (1): 66. doi: 10.3390/toxins15010066 . ISSN   2072-6651. PMC   9867037 . PMID   36668885.