TABLE 2.

Activity at pH 6.2 and 7.3 of a constitutive and pH-regulated promoters isolated from S. gordonii CH1, recorded as the ratio of growth in medium with and without Sp^a

Strain	Activity
	pH 6.2	pH 7.3
CH1 pMM240	0.94 ± 0.01	0.98 ± 0.01
CH1 pMM1221	0.90 ± 0.03	0.99 ± 0.01
CH1 pMM1222	0.73 ± 0.09	0.93 ± 0.03
CH1 pMM1223	0.68 ± 0.05	0.86 ± 0.06
CH1 pMM1224	0.62 ± 0.05	0.82 ± 0.10

^aGrowth was monitored by measuring the absorbance at 620 nm (A₆₂₀) over time, and the mid-log-phase doubling time (t_1/2) was determined. Relative promoter activity at the different pH values is expressed as the ratio of growth in the presence and absence of spectinomycin at each pH tested [t_1/2(+spec)/ t_1/2(−spec)]. pMM240 contains a constitutive promoter of S. gordonii CH1.