A study on the membrane potential and pH gradient in chromatophores and intact cells of photosynthetic bacteria.

Generation of membrane potential (delta psi) and transmembrane pH difference (delta pH) was studied in PPi-energized chromatophores of Rhodospirillum rubrum by means of measurements of carotenoid and bacteriochlorophyll absorption changes, atebrin and 8-anilinonaphthalene-1-sulphonate fluorescence responses, and phenyldicarbaundecaborane transport. The data obtained are consistent with the suggestion that carotenoid, bacteriochlorophyll and phenyldicarbaundecaborane responses are indicators of delta psi, while an atebrin response is an indicator of delta pH. The fluorescence of 8-anilinonaphthalene-1-sulphonate is affected both by delta psi and delta pH.