Calcium signal modulators inhibit aerial mycelium formation in Streptomyces alboniger.

accelerated aerial mycelium formation in various actinomycete species, including S. alboniger. This induction was completely inhibited by ethylene glycol bis(/?-aminoethylether)-JV,N,N ',N '-tetraacetic acid (EGTA), a Ca2+-specific chelating agent. Ca2+ thus has been shown to play a role in aerial mycelium formation of 21 (58%) out of 36 strains of actinomycetes tested3). Ca2+ is known as a second messenger in eukaryotes, mediating physiologically important signals in cell responses such as muscle contraction, hormone secretion, and cell division and proliferation40. Signal mediations via Ca2 + are, in most cases, conducted through the action of calmodulin activated as a result of binding with Ca2+. The Ca2 +/calmodulin signalling processes are regulated by several chemical modulators that have proved powerful tools for analyzing the role of Ca2+/ calmodulin action in cell responses. These modulators therefore could be useful for clarifying the physiological role of Ca2+ in aerial mycelium formation by actinomycetes. Wehere describe the selective inhibititory action of the Ca2 + /calmodulin modulators on aerial mycelium formation by S. alboniger, confirming that Ca2 + functions in aerial mycelium formation. Three types of Ca2+/calmodulin signal modulators were used: Ca2+ channel blockers (verapamil HCl, diltiazem à" HC1 and nifedipine), calmodulin inhibitors (ophiobolin A, prenylamine lactate and chlorpromazine), and a Ca2 + chelator (EGTA). The paper disc bioassay was used to assess their inhibition of aerial mycelium formation by S. alboniger IFO 12738.