Genetic Analysis of Global Regulation of Streptomyces Antibiotics

链霉菌是一组丝状土壤细菌，具有使其成为有吸引力的原核生物的两个特征：它们发育成复杂的、多细胞的、分化的菌落，并产生大量的次生代谢物，其中许多是有用的抗生素。抗生素的产生通常伴随着形态分化，开始于营养生长和孢子前分化菌丝的产生之间的过渡。本研究的长期目标是发现调控抗生素合成的基因，了解它们的功能，并确定它们在控制抗生素基因表达的调控网络中的功能关系。本研究的直接目标是集中在最近发现的三个遗传因子：absA， abb和abc。absa编码信号转导系统的AbsA2应答调节因子对抗生素基因表达全局负调控的机制将通过遗传学、分子遗传学和生化实验来确定：a)确定由AbsA2直接调控的抗生素启动子；b)通过AbsA2表征抑制因子的活性。abb编码的RNaseIII同源物调控抗生素的机制方面将通过抑制因子分析来确定abb调控抗生素的途径元件，并通过评估RNaseIII在抗生素调控中的催化活性来确定。abc操纵子调控抗生素基因表达机制的各个方面将通过定义abc位点mia的120 nt序列如何对抗生素基因表达施加多拷贝抑制来确定，特别是评估其调节因子的强预测。这项研究的结果有望阐明控制链霉菌抗生素合成的调控程序的各个方面，为如何合理操纵抗生素生产提供见解，并扩大我们对微生物多细胞分化的理解。

Streptomycetes, a group of 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 research are focussed on three recently-discovered genetic elements: absA, absB and absC. The mechanism by which the AbsA2 response regulator of the absA-encoded signal transduction system exerts global negative control over antibiotic gene expression will be determined using genetic, molecular genetic, and biochemical experiments to: a) determine the antibiotic promoters that are directly regulated by AbsA2; and b) characterize repressor activity by AbsA2. Aspects of the mechanism by which the absB-encoded RNaseIII homolog regulates antibiotics will be determined using suppressor analysis to identify elements of the pathway through which absB regulates antibiotics and by evaluation of the role of RNaseIII catalytic activity in antibiotic regulation. Aspects of the mechanism by which the absC operon regulates antibiotic gene expression will be determined by defining how a 120 nt sequence of the absC locus, mia, exerts multi-copy inhibition of antibiotic gene expression, especially evaluating the strong prediction that it titrates a regulatory factor. The results of this research promise to elucidate aspects of the regulatory program controlling streptomycete antibiotic synthesis, to provide insights into how antibiotic production might be rationally manipulated, and to expand our understanding of microbial multicellular differentiation.