Analyzing the Developmental Expression of Sigma Factors with S1-Nuclease Mapping

Streptomycetes are mycelial, Gram-positive soil bacteria which produce a variety of biologically active secondary metabolites, including the majority of known antibiotics. In addition to this physiological differentiation, they undergo a complex cycle of morphological differentiation. Spores after germination on solid-growth media form a network of vegetative “substrate mycelium” that grows into the medium. After unknown signal(s), the substrate mycelium differentiates, and white aerial mycelium is formed that grows into the air. Later it undergoes septation and, in the last step of the process, forms chains of spores. The differentiation of Streptomyces is controlled on several levels, of which heterogeneity of σ factors of RNA polymerase seems to play an important role (1 ). Therefore, we examined the Streptomyces differentiation through the study of these key proteins in this process.