pH measurements by 31p NMR in bacterial suspensions using phenyl phosphonate as a probe

Phenylphosphonate was used as an internal reference for 31p NMR measurements of E. coli cytoplasmic pH. Phenylphosphonate diffused into the cells allowing determination of pH, independent of magnetic susceptibility differences between intercellular and extracellular pools. Phenylphosphonate was used to measure pH changes during succinate uptake and metabolism, as well as during uncoupling of the transmembrane pH gradient by pentachlorophenol.