REGULATION OF HISTIDINE UTILIZATION IN BACILLUS SUBTILIS

革兰氏杆菌产孢量的启动和抗生素的产生 土壤中存在枯草芽孢杆菌等阳性芽胞细菌 对营养限制的反应。然而，营养限制也 激活许多降解途径的合成，这些途径提供 在环境压力下生长和适应的营养物质。至 开始了解代谢信号和系统的网络 在营养受限生长过程中调控基因表达 细菌对枯草杆菌组氨酸利用酶的调节 (小屋)正在研究中。HUT酶的表达受 三个独立的调控系统，组氨酸诱导，碳 分解代谢抑制和氨基酸抑制。与之相对的是 产酸克雷伯菌HUT酶，HUT在枯草杆菌中不表达 受氮素限制的生长显著降低。 这些规定所需的顺式代理木屋用地的位置 通过缺失分析鉴定出三个系统。本土化 突变将被用来更准确地定义这些位点。这个 DNA环参与HUT分解代谢抑制的可能性 将通过(I)体内足迹实验来检查表达， 以及(Ii)通过确定是否改变了 这两个顺式作用的分解代谢抑制位点也影响着 分解的压抑。调节分解代谢的交易因素 抑制和氨基酸抑制将通过分离鉴定 在含有以下物质的培养基上生长期间HUT表达发生变化的突变体 要么抑制碳源，要么抑制氨基酸。DNA补充了这些 将对突变体进行克隆和测序。这些研究应该有助于确定 调节土壤细菌中基因表达的范例。在……里面 此外，他们将提供信息和遗传工具 优化药用和农业重要化合物的生产 在这些细菌中通过商业发酵或在 土壤，那里的养分相对稀缺。

The initiation of sporulation and the production of antibiotics in gram- positive sporulating soil bacteria such as Bacillus subtilis occurs in response to nutrient limitation. However, nutrient limitation also activates the synthesis of a number of degradative pathways which provide nutrients for growth and adaptation during environmental stress. To begin to understand the network of metabolic signals and systems that regulate gene expression during nutrient-limited growth in this bacterium, regulation of the B. subtilis histidine utilization enzymes (hut) is being studied. Expression of the hut enzymes is controlled by three independent regulatory systems, histidine induction, carbon catabolite repression and amino acid repression. In contrast to the Klebsiella areogenes hut enzymes, hut expression in B. subtilis is not significantly derepressed by nitrogen-limited growth. The location of the cis-acting hut sites required for regulation by these three systems was identified by deletion analysis. Localization mutagenesis will be used to more precisely define these sites. The possibility that DNA looping is involved in catabolite repression of hut expression will be examined with (i) in vivo footprinting experiments, and (ii) by determining whether mutations that alter the spacing between the two cis-acting catabolite repression sites also affects the level of catabolite repression. transacting factors mediating catabolite repression and amino acid repression will be identified by isolating mutants with altered hut expression during growth on medium containing either repressing carbon sources or amino acids. DNA complementing these mutants will be cloned and sequenced. These studies should help define the paradigms that regulate gene expression in soil bacteria. In addition, they will provide both information and genetic tools for optimizing production of medically and agriculturally important compounds in these bacteria by commercial fermentation or during growth in the soil, where nutrients are relatively scarce.