TABLE 2.

Vacuolating and hemolytic titers of V. cholerae and E. coli strains with recombinant clones^a

Strainb	Test sample	Reciprocal titer of:
		Cell vacuolating activity	Hemolytic activity
V. cholerae CO848b (wild type)	50-Fold-concentrated culture supernatant	1,024	512
V. cholerae CO848b (Strr)	50-Fold-concentrated culture supernatant	1,024	512
V. cholerae CO848b (hlyA::tet)	50-Fold-concentrated culture supernatant	<2c	<2
E. coli DH5α	50-Fold-concentrated culture supernatant	<2	<2
E. coli DH5α	Cell sonicate	<2	<2
E. coli DH5α(pBSC-hlyA)	50-Fold-concentrated culture supernatant	<2	<2
E. coli DH5α(pBSC-hlyA)	Cell sonicate	16	32

^aV. cholerae and E. coli DH5α were grown in 50 ml of AKI medium, and the cell-free culture supernatant was concentrated 50-fold by ultrafiltration and then added to nonconfluent HeLa cells. The bacterial pellet obtained from recombinant E. coli DH5α(pBSC-hlyA) grown in 50 ml of Luria-Bertani medium was sonicated, and then the cell sonicate was added to HeLa cells. 

^bStr^r, Streptomycin resistant; hlyA::tet, hemolysin gene disrupted by tetracycline gene; pBSC-hlyA, plasmid pBluescript with cloned hemolysin (hlyA) gene. 

^cA value of <2 depicts no vacuolating or hemolytic activities.