TABLE 2.

Biological activities of Act produced in culture filtrates of A. hydrophila SSU and its isogenic mutant and revertant

Culture	Hemolytic activitya	Cytotoxic activitya	Enterotoxic activity (μl/cm)b
Wild-type A. hydrophila with native Act	1:512	1:2,048	118 ± 21
E. coli with suicide vector pJQ200c containing a truncated act gene	0	0	NDd
Double-crossover mutant of A. hydrophila with a truncated act gene	0	0	0
Revertant strain of A. hydrophila in which the truncated act gene was replaced with the native act gene	1:512	1:2,048	112 ± 12

^aThe hemolytic and cytotoxic activities were defined as the reciprocal of the highest dilution of the toxin causing 50% lysis of erythrocytes or 50% destruction of CHO cells, respectively. 

^bEnterotoxic activity was determined in mouse ligated intestinal loops. Results are means ± standard deviations. 

^cSuicide vector pJQ200 gives a gentamicin-resistant and sucrose-sensitive phenotype to the cultures. 

^dND, not done.