Streptomyces hormones and corresponding receptors in antibiotic producing industrial Streptomyces species

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Streptomycetes are Gram-positive soil bacteria characterized by their ability to produce numerous kinds of useful secondary metabolites as well as by their complex life cycle including the formation of aerial mycelia and spores. The two characteristic phenotypes have been know to link each other, and low-molecular-weight compounds called γ-butyrolactone autoregulators have been found in some Streptomyces species to regulate the two phenotypes. However, with the Streptomyces strains used for antibiotic production in industrial scale, nothing has been know on the nature of the intrinsic hormones and/or corresponding receptor proteins to regulate the antibiotic production.1. To survey the possible involvement of autoregulators in industrial Streptomyces strains, we used S. fungicidicus which produces enramycin, S. hygroscopicus which produces maridomycin, S. rochei which produces lancacidin, S. albulus which produces cycloheximide, S. antibioticus and S. catenulae which produce actinomycin, S. albogriseolus which produces fibrostatin, Saccharopolyspora eythrae which produces erythromycin, S. triangulatus which produces baumycin, and S. lavendulae which produces mitomycin.2. From the conserved amino acid sequences among several autoregulator receptor proteins, PCR primers were designed. Also, from the barX-type genes which often exist just beside the receptor genes, other set of PCR primers were designed.3. Using these primers, receptor homologs and/or barX homologs were identified in six of the above strains. Seven kbp genomic fragment was cloned from S. triangulatus, and DNA sequencing revealed the presence of genes homologous to receptor and barX.4. The deduced amino acid sequence of the receptor homolog indicated the high homology to IM-2 specific receptor FarA, indicating that S. triangulatus should possesses IM-2 type autoregulator.