Convergence of the secretory pathways for cholera toxin and the filamentous phage, CTX phi

Virulence of Vibrio cholerae depends on secretion of cholera toxin (CT), wh ich is encoded within the genome of a filamentous phage, CTX phi. Release o f CT is mediated by the extracellular protein secretion (eps) type II secre tion system. Here. the outer membrane component of this system, EpsD, was s hown to be required for secretion of the phage as well. Thus, EpsD plays a role both in pathogenicity and in horizontal transfer of a key virulence ge ne. Genomic analysis suggests that additional filamentous phages also explo it chromosome-encoded outer membrane channels.