Baca-DeLancey R R, South M M, Ding X, Rather P N
Department of Medicine, Case Western Reserve University School of Medicine and Research Service, Department of Veterans Affairs, Cleveland, OH 44106, USA.
Proc Natl Acad Sci U S A. 1999 Apr 13;96(8):4610-4. doi: 10.1073/pnas.96.8.4610.
Utilizing the bicistronic reporter transposon mini-Tn5 lacZ-tet/1, we have identified lacZ fusions to four Escherichia coli genes/operons that are strongly activated by the accumulation of self-produced extracellular signals. These fusions were designated cma9, cma48, cma113, and cma114 for conditioned medium activated. Each of the cma fusions was expressed in a growth phase-dependent manner, and the presence of conditioned medium from a stationary phase E. coli culture resulted in the premature activation of these fusions in cells at early to mid-logarithmic phase. The cma48 and cma114 fusions were dependent on RpoS for growth phase expression and response to extracellular factors. The extracellular factors that activated the cma9, cma48, and cma114 fusions were produced in both rich complex and defined minimal media. The cma fusions were shown to be within the cysK (cma9), astD (cma48), tnaB (cma113), and gabT (cma114) genes. These genes function in the uptake, synthesis, or degradation of amino acids that yield pyruvate and succinate.
利用双顺反子报告转座子mini-Tn5 lacZ-tet/1，我们鉴定出了与四个大肠杆菌基因/操纵子的lacZ融合体，这些基因/操纵子会被自身产生的细胞外信号的积累强烈激活。这些融合体被命名为cma9、cma48、cma113和cma114，代表条件培养基激活。每个cma融合体都以生长阶段依赖的方式表达，来自稳定期大肠杆菌培养物的条件培养基的存在导致这些融合体在对数早期至中期的细胞中过早激活。cma48和cma114融合体在生长阶段表达和对细胞外因子的反应方面依赖于RpoS。激活cma9、cma48和cma114融合体的细胞外因子在丰富的复合培养基和确定的基本培养基中均有产生。已证明cma融合体位于cysK（cma9）、astD（cma48）、tnaB（cma113）和gabT（cma114）基因内。这些基因在产生丙酮酸和琥珀酸的氨基酸的摄取、合成或降解中发挥作用。
