Secretion of an Aeromonas hydrophila aerolysin by a mutant strain of Escherichia coli

Abstract Expression of the Aeromonas hydrophila AH2 aerolysin was analysed in 2 mutant derivatives of Escherichia coli 5K that overproduce E. coli haemolysin, encoded by the multicopy plasmid pANN202–312. When plasmid pHPC3–700 carrying the A. hydrophila aerolysin genes was transformed into one of the mutants, Hha-2T, the transformants produced external aerolysin. Neither the parental 5K strain or the other mutant, Hha-1T, showed extracellular aerolysin activity. For strain Hha-2T, the kinetics of external aerolysin production was similar to that previously reported for A. hydrophila AH2. No cell lysis or release of other proteins to the culture medium could be detected for the period of time that strain Hha-2T exported aerolysin into the external medium.