Stimulatory effect of indole-3-acetic acid on aerial mycelium formation and antibiotic production in Streptomyces spp.
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An investigation was conducted to explore the effect of the phytohormone indole-3-acetic acid (IAA) on cellular differentiation in streptomycetes. A total of 21 <I>Streptomyces</I> strains known to produce antibiotics were tested. IAA (1–20 μg/ml) in Bennett's agar markedly stimulated aerial mycelium formation and antibiotic production in 12 and 13 test strains, respectively. The stimulating effect of IAA was confirmed even in a submerged culture: production of an anthracycline group antibiotic, rhodomycin, by <I>S. purpurascens</I> NBRC 13077 cultured in oatmeal-MYM broth, was markedly enhanced by addition of IAA (20 μg/ml). mRNA differential display (RT-PCR) analysis revealed that expression of <I>rdmA</I>, <I>rdmB</I>, <I>rdmC</I>, <I>rdmD</I> and <I>rdmE</I>, all genes involved in rhodomycin production, was up-regulated by IAA treatment in <I>S. purpurascens</I>. These results suggest that IAA may act as a common regulating agent for sporulation and secondary metabolism in streptomycetes.
Actinomycetologica 21(1), 32-39, 2007-06-25
The Society for Actinomycetes Japan