Influence of cyclic AMP on the growth response and anaerobic metabolism of carbon monoxide in Rhodocyclus gelatinosus

Rhodocyclus gelatinosus strain 1 (str. 1), a photoheterotrophic bacterium, used CO as an energy substrate under anaerobic CO/light conditions, and exhibited a diauxic growth response when CO was removed from the culture. Changes in the level of cyclic AMP which occurred in cells during diauxie suggested that the cyclic nucleotide operated as an intracellular control molecule. During CO/light-phase growth, intracellular cyclic AMP was 30 pmol/mg protein, and, as str. 1 adapted for photosynthetic growth after removal of CO, intracellular cyclic AMP levels decreased to 9 pmol/mg protein. In addition to stimulating formation of CO oxidative activity, a high level of cyclic AMP in str. 1 during growth with CO appeared to influence photometabolism negatively by repressing bacteriochlorophyll formation.