Hemolisinas bacterianas

ALBESA INÉS

Adelantos en Microbiología y Enfermedades infecciosas

Ed.Celia Coto, José Esparza y Ramón A.de Torres

Lugar: Caracas- Buenos Aires; Año: 1988; p. 37 - 60

Hemolytic activity has been reported in bacteria of different genera. They were associated with a cytotoxic effect on erythrocytes by means of membrane damage which can results in a rearrangement and disruption of the bilayer; in this case, they are considered cytolysins. The action mechanism of a hemolysin group is done by phospholipase activity on hydrophobic regions of membranes, this enzymatic action causes a perturbation that lyses erythrocytes of different animals species. The behavior of other bacterial hemolysins tends to resemble that of detergents, because they have a very strong activity on surface, they have relatively low specific hemolytic effect and exhibit a brad spectrum of sensitive cells, without preference for a particular erythrocyte species. A third group of hemolysins encloses the lysisns activated by SH compounds, sometimes called ?oxygen-labile hemolysins?, they share common properties; all of them are irreversibly inactivated by low concentrations of cholesterol, the oxygen effect can be abolished by reducing agents, they are immunological related to one another and the temperature reduces their activity. The SH form of these lysins is active, -S-S- form obtained by oxidation is an active and does not interact with erythrocytes. Cholesterol represents the primary lysine acceptor of membrane, but there are some differences among the thiol-dependent cytolisins in: the reversibility of binding to membrane, the activity at 0ºC and the damage caused in membranes with distinct leakage of cytoplasmic material into the surrounding medium. The biggest group of hemolysins includes the lysins with an unknown mode of action, it compresses cytolysins of Gram-negative and Gram-positive bacteria. Although the mechanism of cell damage were studied by many investigators, the majority of hemolysin action mechanism must be discovered. In the last years it was proposed that some bacterial lysins can act like other substances that perturb the membrane integrity by a important and very widespread mechanism of formation of transmembrane pores, with insertion of alien proteins into the lipid bilayer. When more hemolysins will be detected new characteristics and mode of action will be described, and the role of hemolysins in pathogeny will be best understood.