TABLE 1.

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

Expt no.SystemaAddition% SurvivalExternal pHbInternal pHcΔpHΔψc (mV)PMF (mV)
1Log phaseNoneNDd6.9 ± 0.2e7.8 ± 0.1−53 ± 4−86 ± 3−139
Stationary phaseNoneND6.8 ± 0.27.6 ± 0.1−44 ± 4−52 ± 6−96
2AR2None<0.12.3 ± 0.03.6 ± 0.1−73 ± 5−5 ± 4−78
Glutamate1002.5 ± 0.14.2 ± 0.1−108 ± 630 ± 6−78
3AR3None<0.12.4 ± 0.13.7 ± 0.1−80 ± 74 ± 1−76
Arginine752.6 ± 0.14.7 ± 0.1−128 ± 281 ± 17−47
  • a Cells 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.

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

  • c Internal pH and Δψ were measured after 30 min of acid challenge.

  • d ND, not determined.

  • e Standard error of the mean.