Table 1. Proton-binding sites and phosphate groups in the cell envelope and membrane potential of S. aureus strains.

Strain	Proton-binding site concentrations (µmol/mg bacteria)	Detection of phosphate group absorption bands by FTIR (cm−1)	Membrane potential (mV)
Wild type	35.6	1. C-O-P-O-C stretch (1061 cm−1)a2. PO2 − antisymmetric stretch (1235 cm−1)a	−123
ΔtagO	27.5	Bdb	−120
ΔtagO complemented	35.4	Ndc	−122

^a, Assignment was made according to those reported previously in [42].

^b, Bd, below detection limit.

^c, Nd, not determined.