Bioassay for the isolation of Dictyostelium discoideum mutants deficient in extracellular accumulation of cyclic adenosine 3',5'-monophosphate.

The growth response to external cyclic adenosine 3',5'-monophosphate of a strain of Escherichia coli deleted for adenyl cyclase was utilized to screen for mutants of Dictyostelium discoideum unable to accumulate this chemical extracellularly. The threshold amount of cyclic adenosine 3',5'-monophosphate able to induce growth of this bacterium was 3 to 4 mug/ml at 37 C and approximately 25 mug/ml at 27 C. Conditions are described that permit the detection of as low as 2 mug of this chemical at either temperature.