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Release of the type I secreted α‐haemolysin via outer membrane vesicles from Escherichia coli
Author(s) -
Balsalobre Carlos,
Silván Jose Manuel,
Berglund Stina,
Mizunoe Yoshimitsu,
Uhlin Bernt Eric,
Wai Sun Nyunt
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04938.x
Subject(s) - hemolysin , biology , bacterial outer membrane , periplasmic space , secretion , escherichia coli , microbiology and biotechnology , virulence , extracellular , vesicle , virulence factor , bacteria , hemolysis , enterobacteriaceae , biochemistry , membrane , gene , genetics , immunology
Summary The α‐haemolysin is an important virulence factor commonly expressed by extraintestinal pathogenic Escherichia coli . The secretion of the α‐haemolysin is mediated by the type I secretion system and the toxin reaches the extracellular space without the formation of periplasmic intermediates presumably in a soluble form. Surprisingly, we found that a fraction of this type I secreted protein is located within outer membrane vesicles (OMVs) that are released by the bacteria. The α‐haemolysin appeared very tightly associated with the OMVs as judged by dissociation assays and proteinase susceptibility tests. The α‐haemolysin in OMVs was cytotoxically active and caused lysis of red blood cells. The OMVs containing the α‐haemolysin were distinct from the OMVs not containing α‐haemolysin, showing a lower density. Furthermore, they differed in protein composition and one component of the type I secretion system, the TolC protein, was found in the lower density vesicles. Studies of natural isolates of E. coli demonstrated that the localization of α‐haemolysin in OMVs is a common feature among haemolytic strains. We propose an alternative pathway for the transport of the type I secreted α‐haemolysin from the bacteria to the host cells during bacterial infections.