TABLE 3.

Concentration of CT in culture media after growth in inducing conditions or in T84 medium

Straina	Growth conditions	[CT] (nM)b
O395	LB, 30°C, overnight, rolling	205
O395NT	LB, 30°C, overnight, rolling	0
O395	T84 medium, 37°C, 4 h, static	15.7
O395NT	T84 medium, 37°C, 4 h, static	0
P27459	AKI, 37°C, overnight, shaking	11
P4	AKI, 37°C, overnight, shaking	0
P27459	T84 medium, 37°C, 4 h, static	0.060
P4	T84 medium, 37°C, 4 h, static	0

^aO395NT and P4 are derivatives of O395 and P27459, respectively, with deletions of ctxA and ctxB genes. 

^bCT was measured by the GM₁-ganglioside enzyme-linked immunosorbent assay with commercially available CT (Sigma) used for a standard curve.