GENES INDUCED BY PH PERTURBATION ON ESCHERICHIA COLI

响应于外部pH（"外部pH"）扰动的基因 刺激子”）和内部pH的扰动（“内部pH 刺激子"）将在大肠杆菌中定义。 两个不同 pH敏感的lacZ融合菌株的种类已经被 分离的：（A）通过降低外部pH可诱导的菌株，但不 通过在稳定的pH下加入膜可渗透的弱酸， 和（B）由弱酸介导的降低 内部pH值，而不是外部;酸化。 融合菌株 通过pH筛选方法分离， Slonczewski，使用MudI1734产生的Mud-fusion池 (lac，Km）构建了一个由M.卡萨达班 的程度 诱导范围从10倍到800倍。 此前， 没有公开的关于酸性诱导的基因融合菌株的报道， 也没有报告说基因是由内部而不是外部诱导的 pH扰动（Booth，1985年） pH敏感性基因座的特征在于 遗传学和生物化学。 将寻找更多的突变体 其表现出通过外部和外部的碱性扰动的诱导， 内部pH值。可以定义单独的"刺激物"， 对于对外部和内部碱化反应的基因， 以及外部和内部的酸化。 pH响应基因融合菌株的厌氧反应 会得到考验 由于跨膜pH差（Δ pH） 对质子势有贡献，人们可能会期望一些酸- 诱导基因被包括在厌氧刺激子中。 还将检测已知厌氧基因的pH诱导性。 将进行双向凝胶电泳分析 在酸性培养基中生长诱导的蛋白质（外部酸胁迫） 或在膜可渗透的弱酸（内部）存在下 酸胁迫）。 将进行类似的实验以检测 碱胁迫诱导的基因。

Genes responsive to perturbation of external pH (an "external pH stimulon") and to perturbation of internal pH (an "internal pH stimulon") will be defined in Escherichia coli. Two distinct classes of pH-sensitive lacZ fusion strains have already been isolated: (A) strains inducible by lowering of external pH, but not by addition of a membrane-permeable weak acid at steady pH, and (B) strains inducible by weak-acid-mediate lowering of internal pH, but not by external; acidification. The fusion strains were isolated through pH screening methods devised by Slonczewski, using a Mud-fusion pool generated with MudI1734 (lac, Km), a vector constructed by M. Casadaban. Their degree of induction ranges from 10-fold to 800-fold. Previously, there are no published reports of gene fusion strains inducible by acidity, and no reports of genes induced by internal but not external perturbation of pH (Booth, 1985.) The pH-sensitive loci will be characterized with respect to genetics and biochemistry. Additional mutants will be sought which exhibit induction by alkaline perturbation of external and of internal pH. It may be that separate "stimulons" can be defined for genes responsive to alkalinization, external and internal, as well as to acidification, external and internal. The anaerobiosis response of pH-responsive gene fusion strains will be tested. Since the transmembrane pH difference (delta pH) contributes to the proton potential, one might expect some acid- inducible genes to be included in the anaerobiosis stimulon. Known anaerobiosis genes will also be tested for pH-inducibility. Two-dimensional gel electrophoresis will be perforemd to analyze proteins induced by growth in acid medium (external acid stress) or in the presence of a membrane-permeable weak acid (internal acid stress). Similar experiments will be performed to detect genes induced by alkaline stress.