Cloning and expression of Vibrio cholerae virulence gene, accessory cholera enterotoxin (ace)

The cholera enterotoxin (CT) has been considered a major virulence factor of Vibrio cholerae. The accessory cholera enterotoxin (ace) gene is the third gene of V. cholerae virulence cassette. The gene coding for the Ace toxin was amplified from V. cholerae isolates producing a single band of 314 bp. The presence of ace gene was confirmed by hybridization as well as by sequencing. The gene was successfully expressed in Escherichia coli (LMG194) using expression, pBAD/Thio-TOPO vector. Optimal conditions for expression included choice of host strain, temperature used for culturing, and concentration of antibiotic and arabinose inducer. The Ace protein was obtained from the cell supernatant as a fusion protein with a molecular mass 34 kDa which was detected using an anti V5-HRP epitope tagged antibody.