FIG. 1.

Cartoon representing the two-phase culture system for in vivo labeling of Streptomyces strains by radioactive compounds (a) and a side view of a Streptomyces culture growing on glass beads (b). The bigger syringe in panel a containing the glass bead layer serves as an artificial habitat for growth of streptomycetes. To initiate labeling, the smaller syringe functions as a pump to withdraw spent medium and inject it back after supplementing radioactivity. The spent medium can similarly be modified or supplemented with signal molecules. During development, the submerged hyphae shown on panel b probably undergo lysis through an orderly process and serve as a source of nutrients for emerging aerial mycelium (15).