Champness 9604055 Streptomycetes, filamentous soil bacteria, possess two characteristics that make them attractive prokaryotes for study: they develop into complex, multicellular, differentiated colonies and they produce a vast array of secondary metabolites, many of which are useful as antibiotics. Antibiotic production is usually coupled to morphological differentiation, beginning at the transition between vegetative growth and production of pre-spore differentiated hyphae. The long term goal of this research is to discover the genes that regulate antibiotic synthesis, to understand how they function, and to determine their functional relationships in the regulatory network controlling antibiotic gene expression. The immediate objectives of this proposal focus on three genetic elements discovered in previous NSF funding periods: absA, absB and mia. Research will proceed along the following lines: 1. The mechanism by which the absA-encoded signal transduction system exerts global negative control over antibiotic gene expression will be determined. Genetic, molecular genetic and biochemical experiments will: a) characterize functionally important regions and interactions of the AbsA1/A2 "sensor-kinase" and response regulator proteins; b) establish the role of protein phosphorylation in AbsA-mediated regulation; and c) explore the genetic pathway through which absA regulates expression of the antibiotic "pathway-specific regulators." 2. The absB gene and its probable gene product, an RNaseIII, will be characterized through determination of the RNaseIII (absB) null phenotype, functional studies on the S. coelicolor RNaseIII, and identification of candidate RNaseIII targets. 3. The 190 nt mia sequence, which exerts multi-copy inhibition of antibiotic gene expression, will be characterized to determine the functional regions of the sequence. The results of the proposed work promise to elucidate aspec ts of the regulatory programs controlling streptomycete gene expression, and to expand our understanding of microbial multicellular differentiation.
