This article may be too technical for most readers to understand.(April 2016)
Tolaasin, a toxic secretion by Pseudomonas tolaasii , is the cause of bacterial brown blotch disease of edible mushrooms.Tolaasin is composed of 18 amino acids, including a beta-hydroxy-octanoic acid chain located at the N terminus. 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. At high concentrations, tolaasin acts as a detergent that is able to directly dissolve eukaryotic membranes. The fungal cell membranes are disrupted by the lipopeptides through the formation of trans-membrane pores. 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.
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.
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.
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.
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.
Anthrax toxin is a three-protein exotoxin secreted by virulent strains of the bacterium, Bacillus anthracis—the causative agent of anthrax. The toxin was first discovered by Harry Smith in 1954. Anthrax toxin is composed of a cell-binding protein, known as protective antigen (PA), and two enzyme components, called edema factor (EF) and lethal factor (LF). These three protein components act together to impart their physiological effects. Assembled complexes containing the toxin components are endocytosed. In the endosome, the enzymatic components of the toxin translocate into the cytoplasm of a target cell. Once in the cytosol, the enzymatic components of the toxin disrupts various immune cell functions, namely cellular signaling and cell migration. The toxin may even induce cell lysis, as is observed for macrophage cells. Anthrax toxin allows the bacteria to evade the immune system, proliferate, and ultimately kill the host animal. Research on anthrax toxin also provides insight into the generation of macromolecular assemblies, and on protein translocation, pore formation, endocytosis, and other biochemical processes.
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.
Pore-forming proteins are usually produced by bacteria, and include a number of protein exotoxins but may also be produced by other organisms such as apple snails that produce perivitellin-2 or earthworms, who produce lysenin. They are frequently cytotoxic, as they create unregulated pores in the membrane of targeted cells.
Hemolysins or haemolysins are lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane. Although the lytic activity of some microbe-derived hemolysins on red blood cells may be of great importance for nutrient acquisition, many hemolysins produced by pathogens do not cause significant destruction of red blood cells during infection. However, hemolysins are often capable of lysing red blood cells in vitro.
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.
Pseudomonas costantinii is a Gram-negative bacterium that causes brown blotch disease in cultivated mushrooms. It demonstrates hemolytic activity. The type strain is CFBP 5705.
Agaricus bitorquis, commonly known as torq, banded agaric, spring agaric, banded agaricus, urban agaricus, or pavement mushroom, is an edible white mushroom of the genus Agaricus, similar to the common button mushroom that is sold commercially. The name supersedes Agaricus rodmani.
Phallolysin is a protein found the Amanita phalloides species of the Amanita genus of mushrooms, the species commonly known as the death cap mushroom. The protein is toxic and causes cytolysis in many cells found in animals and is noted for its hemolytic properties. It was one of the first toxins discovered in Amanita phalloides when the various toxins in the species where first being researched. The protein itself is observed to come in 3 variations, with observed differences in isoelectric point. Cytolysis can be best described as being the destruction of cells, likely due to exposure from an external source such as pathogens and toxins. Hemolysis then follows a similar destructive pathway, but instead focuses specifically on the destruction of red blood cells. Phallolysin is known to be thermolabile, meaning that it is destroyed at high temperatures, and acid labile, meaning that it is easily broken down in acidic environments.
The Membrane Attack Complex/Perforin (MACPF) superfamily, sometimes referred to as the MACPF/CDC superfamily, is named after a domain that is common to the membrane attack complex (MAC) proteins of the complement system and perforin (PF). Members of this protein family are pore-forming toxins (PFTs). In eukaryotes, MACPF proteins play a role in immunity and development.
Clostridium difficile toxin B is a cytotoxin produced by the bacteria Clostridioides difficile, formerly known as Clostridium difficile. It is one of two major kinds of toxins produced by C. difficile, the other being a related enterotoxin. Both are very potent and lethal.
Microbial toxins are toxins produced by micro-organisms, including bacteria, fungi, protozoa, dinoflagellates, and viruses. Many microbial toxins promote infection and disease by directly damaging host tissues and by disabling the immune system. Endotoxins most commonly refer to the lipopolysaccharide (LPS) or lipooligosaccharide (LOS) that are in the outer plasma membrane of Gram-negative bacteria. The botulinum toxin, which is primarily produced by Clostridium botulinum and less frequently by other Clostridium species, is the most toxic substance known in the world. However, microbial toxins also have important uses in medical science and research. Currently, new methods of detecting bacterial toxins are being developed to better isolate and understand these toxins. Potential applications of toxin research include combating microbial virulence, the development of novel anticancer drugs and other medicines, and the use of toxins as tools in neurobiology and cellular biology.
Tricholoma ustale, commonly known as the burnt knight, is a species of mushroom in the large genus Tricholoma. It is found in Asia, Europe, and North America, though those from North America may represent one or more different species.
Verticillium dry bubble, recently named Lecanicillium fungicola, is a mycoparasite that attacks white button mushrooms, among other hosts, during its generative period. L. fungicola infects the casing layer on the cap structure of several edible mushrooms. This fungal pathogen does not typically infect wild mushrooms, but more commonly cultivated mushrooms are infected such as A. bisporus, which are typically grown in large quantities. Severity of disease depends on several factors, including timing of infection and environmental conditions. Dry bubble follows the typical verticillium life cycle, although insect vectors play a large role in the spread of this disease. Control for L. fungicola is limited, and strict measures must be taken to prevent the spread of infection. L. fungicola is a devastating pathogen in the mushroom industry and causes significant losses in the commercial production of its main host A. bisporus. Annual costs for mushroom growers are estimated at 2–4% of total revenue.
Brown blotch disease is a bacterial infection that affects nearly every species of mushroom. The infecting bacteria, Pseudomonas tolaasii, produces the toxin tolaasin that causes brown spots to cover the surface of the mushroom. Brown blotch disease is especially problematic on common mushroom farms, where it can spread quickly and cause huge economic losses.
The ion channel hypothesis of Alzheimer’s disease (AD), also known as the channel hypothesis or the amyloid beta ion channel hypothesis, is a more recent variant of the amyloid hypothesis of AD, which identifies amyloid beta (Aβ) as the underlying cause of neurotoxicity seen in AD. While the traditional formulation of the amyloid hypothesis pinpoints insoluble, fibrillar aggregates of Aβ as the basis of disruption of calcium ion homeostasis and subsequent apoptosis in AD, the ion channel hypothesis in 1993 introduced the possibility of an ion-channel-forming oligomer of soluble, non-fibrillar Aβ as the cytotoxic species allowing unregulated calcium influx into neurons in AD.
Modeccin is a toxic lectin, a group of glycoproteins capable of binding specifically to sugar moieties. Different toxic lectins are present in seeds of different origin. Modeccin is found in the roots of the African plant Adenia digitata. These roots are often mistaken for edible roots, which has led to some cases of intoxication. Sometimes the fruit is eaten, or a root extract is drunk as a manner of suicide.