TABLE 1.

Effects of AR2 and AR3 on Δψ during acid challenge of EK227

Expt no.	Systema	Addition	% Survival	External pHb	Internal pHc	ΔpH	Δψc (mV)	PMF (mV)
1	Log phase	None	NDd	6.9 ± 0.2e	7.8 ± 0.1	−53 ± 4	−86 ± 3	−139
	Stationary phase	None	ND	6.8 ± 0.2	7.6 ± 0.1	−44 ± 4	−52 ± 6	−96
2	AR2	None	<0.1	2.3 ± 0.0	3.6 ± 0.1	−73 ± 5	−5 ± 4	−78
		Glutamate	100	2.5 ± 0.1	4.2 ± 0.1	−108 ± 6	30 ± 6	−78
3	AR3	None	<0.1	2.4 ± 0.1	3.7 ± 0.1	−80 ± 7	4 ± 1	−76
		Arginine	75	2.6 ± 0.1	4.7 ± 0.1	−128 ± 2	81 ± 17	−47

^aCells used in experiments 1 and 2 were grown in LBG medium to induce AR2. Cells used in experiment 3 were grown in BHIG to induce AR3.

^bStarting external pH values were the same with and without glutamate, but the decarboxylation of glutamate over 30 min raised external pH slightly.

^cInternal pH and Δψ were measured after 30 min of acid challenge.

^dND, not determined.

^eStandard error of the mean.