The effect of light on morphogenesis of Dictyostelium mucoroides

The effect of light on the production of macrocysts and sorocarps of Dictyostelium mucoroides, strain DM-7, has been studied with surface cultures grown on dilute lactose-peptone agar at 22 degrees C with Escherichia coli, strain B/r, as food bacteria. The production of sorocarps or macrocysts can be controlled by altering the light component of the environment. Far red light had no effect on macrocyst production, whereas visible light from 440 to 700 nm inhibited macrocyst production with production decreasing with increasing light intensity. Fluence response curves for macrocyst production were determined for twelve wavelengths of light between 400 and 700 nm. An action spectrum calculated from the fluence response curves shows a single major peak at about 425-430 nm.