Bacterial hemolysin

Herbert and Todd (54) and Bernheimer (7) have expressed the view that many of the bacterial hemolysins may be enzymes. In only one case, however, namely the lecithinase or lethal toxin of Cl. welchii, is the substrate for an hemolysin known (82). 

Bacterial pore-forming proteins, such as oc-hemolysin, secreted by Staphylococcus aureus can be modified so that pore formation is activated by chemical, biochemical, or physical triggers. Such hemolysins, when targeted to tumors, could increase tumor permeability, and hence susceptibility to various cytotoxic drugs (78). 

RTX family of bacterial toxins, which are a gronp of cytolysins and cyto-toxins. Hemolysin (HlyA) is often quoted as the model for RTX toxins. See Coote, J.G., Structural and functional relationship among the RTX toxin determinants of Gram-negative bacteria, FEMS Microbiol. Rev. 8, 137-161, 1992. 

Bhakdi S, Bayley H, Valeva A etal. (1996) Staphylococcal alpha-toxin, streptolysin O, and Escherichia coli hemolysin prototypes of pore forming bacterial cytoly-sins. In Arch Microbiol 165 73-79. 

Hemolysins, which lyse vertebrate erythrocytes, are important virulence factors in vertebrate bacterial pathogens. Such toxins are also found in some Bt strains and seem to be identical to the hemolysin found in B. cereus. Some Bt isolates have been found to produce the same type of diarrhea-producing enterotoxins as B. cereus. Bt may therefore have implications in causing gastroenteritis. 

Bacterial toxins can be classified as membrane-damaging. This group includes escherichia coli (hemolysins), aeromonas, pseudomonas, and staphylococcus alpha... 

Often, less intense reactions are encountered. The epidermolytic, exfoliative toxins A and B attack the epidermidis causing epidermal necrosis (e.g., Sap/tytococcMX-scalded skin syndrome) [9]. Membrane-damaging toxins at infection sites (e.g., a-toxin, a-hemolysin) are a major factor in tissue damage after bacterial adherence has occurred. Other exoproteins, such as proteases, collage-nase, hyaluronidase, and lipase, act as virulence enhancers but do not actively destroy host tissues. 

Other bacterial toxins, classified generally as membrane-damaging, are derived from Escherichia coli (which produces hemolysins), Aeromonas, Pseudomonas, and Staphylococcus, (which also pro-... 

One of the most famous examples are probably the ion channels, such as the Cl channel or the Na, or Ca " channels that allow ion flux across a membrane through water-filled pores, or the aquaporins that allow the passage of water molecules across biological membranes. a-Hemolysin, a bacterial toxin, is another example of a channel-forming protein assembly that can form pores in the membrane of a cell through which ions can leak and eventually kill the cell. Another example are the porins OmpF and PhoE, tubular protein assemblies in the outer membranes of Gram-negative bacteria that allow the transport of nutrients and waste. 

Recently, Bernheimer (7) has studied the kinetics of red cell lysis by a number of hemolytic agents, several of which were of bacterial origin. The results provide a basis for classification of hemolysins. Thus the maximum rate of hemoglobin liberation was found to be a linear function of concentration for pneumolysin, tetanolysin, streptolysin S and toxin. With saponin, various detergents such as cetylpyridinium chloride and tyrocidine and with lecithin-airoa venom mixture or strep-... 

Jean, A.T.S., Swofford, C.A., Panteli, J.T., Brentzel, Z.J., Forbes, N.S., 2014. Bacterial delivery of Staphylococcus aureus a-hemolysin causes regression and necrosis in murine tumors. Mol. Ther. 22, 1266-1274. 

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