Effect of dibutyryladenosine 3':5'-cyclic monophosphate on growth and differentiation in Caulobacter crescentus

Caulobacter crescentus goes through a series of morphological changes during its life cycle, including the coincident expression of synthesis of flagella, pili, and receptor sites for DNA bacteriophage. Upon transfer of a mixed population of cells to medium containing lactose as the sole carbon source, these changes were blocked for about 20 hr until beta-galactosidase activity became apparent. The addition of dibutyryl cyclic AMP to the blocked cultures brought about the resumption of cell differentiation, growth, and the appearance of beta-galactosidase activity within 1 hr. Unlike Escherichia coli, the intracellular and extracellular concentrations of cyclic AMP in C. crescentus did not vary under several growth conditions, including catabolite repression. It would appear, therefore, that although there is an effect of cyclic AMP on the induction of beta-galactosidase and differentiation in C. crescentus, regulation of these processes occurs without consistent changes in the cellular level of this nucleotide.