Alternative secretion mechanism of alpha hemolysin of E. coli by membrane blebs

M.F. HENNING; V.HERLAX; L.BAKÁS

Pinamar, Argentina

Congreso; Reunión X de PABMB y XLI de SAIB; 2005

PABMB, SAIB y SAN

Alpha hemolysin is an important virulence factor produced by several strains of Escherichia coli involved in human extraintestinal diseases, like urinary tract infections, peritonitis, meningitis and septicemia. An operon composed by 4 genes (hlyA, B, C and D) are involved in synthesis of polypeptide, postraslational modification and secretion of the active toxin to extracellular media. The secretion apparatus comprises  HlyB and HlyD and TolC. However, Gram negative cells walls have a dynamics features: outer membrane vesicles (OMVs) are constantly being discharged from the surface of the cell during bacterial growth. This study shows the presence of HlyA on OMVs isolated from culture supernatans supplemented with cyclodextrin in order to enhance the levels of OMVs. OMVs characterized by electron microscopy are bilayered membranous structures, spherical with 50-250 nm diameter composed by phospholipid, lipopolysacharide and proteins. The presence of HlyA on OMV was detected by Western Inmunoblot and the hemolytic activity was tested by hemolytic assays employing sheep blood. OMVs could provide an alternative route for the delivery of HlyA and moreover an alternative mechanism of interaction between HlyA and target cells.