Influence of cyclic AMP on photosynthetic development in Rhodospirillum rubrum.

During O2-free growth in the light and in medium with pyruvate, Rhodospirillum rubrum exhibits diauxic growth. The cells first fermented pyruvate and afterwards photometabolized. Exogenous cyclic AMP acted to prolong the lag period between fermentative and photosynthetic development, as well as to slow the light-dependent growth rate. This observation, and in situ changes in the cyclic AMP levels in cells undergoing biphasic growth, suggested that the cyclic nucleotide was involved in photosynthetic differentiation, perhaps by repressing the formation of the bacteriochlorophyll needed to support growth in the light.