Proton gradients during salt adaptation of Synechococcus.

The ability of cells to energize their membranes during salt-adaptation as measured by delta pH was studied using the electron spin resonance (ESR) spin probe technique. Salt-adaptated cells have the following features: an increased stability of delta pH across the cytoplasmic membrane and a significantly lower rate of delta pH formation across the thylakoid membrane. Therefore, during salt-adaptation, the cytoplasmic membrane takes over the role of primary energizing membrane from the thylakoid membrane. In contrast to non-adapted cells, delta pH across the thylakoid membrane of salt-grown cells is higher under respiratory than under photosynthetic conditions.