TABLE 2.

In vitro CtxB expression under the control of various promoters^a

Promoter/plasmid	Mean CtxB expression (μg/ml/OD600) ± SE
	Temp (°C)				With 0.150 mM 2-2′-dipyridyl
	25	30	37	42
tacp/pETR1	0.67 ± 0.67	4.64 ± 2.82	1.93 ± 0.8	0	—
htpGp/pETR13	0	0	0.6 ± 0.04	0	—
irgAp/pETR12	—	—	0.120 ± 0.007	—	4.50 ± 1.10
Control (pMCSETR1Bb)	0	0	0	0	0

^aAll experiments were performed in V. cholerae Peru2. Peru2(pETR1) and Peru2(pETR13) were grown at indicated temperatures. Peru2(pETR12) was grown at 37°C without or with 0.150 mM 2,2′-dipyridyl (an iron chelator). —, not determined. 

^bContains a promoterless ctxB gene.