TABLE 3.

Effect of lactate on the proton motive force

Strain	Acid	Temp (°C)	pHoa	pHib	ΔpHc	ZΔpHd	ΔΨe	Δpf
NCTC 12900	l-Lactate	37	3.76	4.90	1.14	70.68	−42.92	−113.60
	d-Lactate	37	3.84	4.86	1.02	63.05	−37.54	−100.63
F318	l-Lactate	37	3.81	4.34	0.53	32.65	−20.35	−53.00
	d-Lactate	37	3.79	4.30	0.51	31.62	−25.01	−56.63

^apH_o, external pH in pH units.

^bpH_i values (pH units) are the average of three to five repeat experiments.

^cpH gradient (pH_i − pH_o) expressed in pH units.

^dpH gradient expressed in millivolts, where Z is 62 at 37°C and 58 at 20°C.

^eMembrane potentials, expressed in millivolts, are the average of three to five repeat experiments.

^fProton motive force expressed in millivolts (ΔΨ − ZΔpH).