Purification of an extracellular signaling molecule involved in production of aerial mycelium by Streptomyces coelicolor.

We have extensively purified a factor from conditioned medium that restores aerial mycelium formation to a mutant of Streptomyces coelicolor that is defective in morphological differentiation. Response to this factor is shown to depend on the presence of the BldK oligopeptide import system. We suggest that this substance acts at the first step in a putative cascade of developmental regulatory signals.