Cell-cycle-specific oscillation in the composition of chromatophore membrane in Rhodospirillum rubrum.

Synchrony in phototrophic cultures of Rhodospirillum rubrum was induced by stationary-phase cycling or by alterations in light intensity. Intracytoplasmic chromatophore membranes were prepared by differential centrifugation. Analysis of the composition of chromatophores obtained from cells at different times indicated that the protein/bacteriochlorophyll a ratio was constant throughout the cell cycle but that the protein/phospholipid ratio oscillated. This cell-cycle-dependent fluctuation in chromatophore membrane composition was reflected in the buoyant densities of the isolated chromatophores.