Contact-Dependent Growth Inhibition Causes Reversible Metabolic Downregulation in Escherichia coli
Contact-Dependent Growth Inhibition Causes Reversible Metabolic Downregulation in Escherichia coli
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DOI：
10.1128/jb.01437-08
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发表时间：
2009-03-15
影响因子：
3.2
通讯作者：
Low, D. A.
中科院分区：
文献类型：
--
作者：
Aoki, S. K.;Webb, J. S.;Low, D. A.
接触依赖性生长抑制（CDI）是在大肠杆菌中鉴定的一种机制，通过该机制，表达由cdiA和cdiB编码的双配偶体分泌蛋白的细菌与靶细胞外膜中的BamA结合并抑制其生长。该簇中的第三个基因cdiI编码一种小蛋白质，该蛋白质是赋予对CDI的免疫力所必需和足够的，从而防止表达cdiBA基因的细胞抑制自身生长。在这项研究中，cdiI基因被置于araBAD启动子控制下，以调节免疫蛋白的水平，从而通过去除阿拉伯糖诱导CDI。该CDI自抑制系统用于单种群大肠杆菌的代谢分析。coli细胞进行CDI。接触抑制的细胞表现出改变的细胞形态，包括细丝的存在。值得注意的是，CDI是可逆的，如通过在诱导CDII免疫蛋白后恢复细胞生长和正常细胞形态所证明的。从CDI中回收细胞还需要能量来源。经历CDI的细胞显示出代谢参数显着、可逆的下调，包括有氧呼吸、质子动力（Delta p）和稳态ATP水平。目前尚不清楚呼吸和/或Δ p的减少是否直接参与生长抑制，但使用atp突变体排除了ATP在CDI机制中的作用。与观察到的Δ p降低一致，基于pspA mRNA水平的分析，在经历CDI的细胞中诱导了噬菌体休克应答，但在恢复细胞中未诱导。
Contact-dependent growth inhibition (CDI) is a mechanism identified in Escherichia coli by which bacteria expressing two-partner secretion proteins encoded by cdiA and cdiB bind to BamA in the outer membranes of target cells and inhibit their growth. A third gene in the cluster, cdiI, encodes a small protein that is necessary and sufficient to confer immunity to CDI, thereby preventing cells expressing the cdiBA genes from inhibiting their own growth. In this study, the cdiI gene was placed under araBAD promoter control to modulate levels of the immunity protein and thereby induce CDI by removal of arabinose. This CDI autoinhibition system was used for metabolic analyses of a single population of E. coli cells undergoing CDI. Contact-inhibited cells showed altered cell morphology, including the presence of filaments. Notably, CDI was reversible, as evidenced by resumption of cell growth and normal cellular morphology following induction of the CdiI immunity protein. Recovery of cells from CDI also required an energy source. Cells undergoing CDI showed a significant, reversible downregulation of metabolic parameters, including aerobic respiration, proton motive force (Delta p), and steady-state ATP levels. It is unclear whether the decrease in respiration and/or Delta p is directly involved in growth inhibition, but a role for ATP in the CDI mechanism was ruled out using an atp mutant. Consistent with the observed decrease in Delta p, the phage shock response was induced in cells undergoing CDI but not in recovering cells, based on analysis of levels of pspA mRNA.