Salzberg Letal I, Helmann John D
Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA.
J Bacteriol. 2008 Dec;190(23):7797-807. doi: 10.1128/JB.00720-08. Epub 2008 Sep 26.
The Bacillus subtilis membrane contains diacylglycerol-based lipids with at least five distinct headgroups that together help to define the physical and chemical properties of the lipid bilayer. Here, we describe the phenotypic characterization of mutant strains lacking one or more of the following lipids: glycolipids (ugtP mutants), phosphatidylethanolamine (pssA and psd mutants), lysylphosphatidylglycerol (mprF), and cardiolipin (ywnE and ywjE). Alterations of membrane lipid headgroup composition are generally well-tolerated by the cell, and even severe alterations lead to only modest effects on growth proficiency. Mutants with decreased levels of positively charged lipids display an increased sensitivity to cationic antimicrobial compounds, and cells lacking glycolipids are more sensitive to the peptide antibiotic sublancin and are defective in swarming motility. A quadruple mutant strain (ugtP pssA mprF ywnE), with a membrane comprised predominantly of phosphatidylglycerol, is viable and grows at near-wild-type rates, although it forms long, coiled filaments. Transcriptome comparisons identified numerous regulons with altered expression in cells of the ugtP mutant, the pssA mprF ywnE triple mutant, and the ugtP pssA mprF ywnE quadruple mutant. These effects included a general decrease in expression of the SigD and FapR regulons and increased expression of cell envelope stress responses mediated by sigma(M) and the YvrGHb two-component system.
枯草芽孢杆菌的细胞膜含有基于二酰甘油的脂质，其具有至少五种不同的头部基团，这些头部基团共同有助于定义脂质双层的物理和化学性质。在这里，我们描述了缺乏以下一种或多种脂质的突变菌株的表型特征：糖脂（ugtP突变体）、磷脂酰乙醇胺（pssA和psd突变体）、赖氨酰磷脂酰甘油（mprF）和心磷脂（ywnE和ywjE）。细胞膜脂质头部基团组成的改变通常能被细胞很好地耐受，即使是严重的改变也只会对生长能力产生适度的影响。带正电荷脂质水平降低的突变体对阳离子抗菌化合物的敏感性增加，缺乏糖脂的细胞对肽抗生素枯草菌素更敏感，并且在群体运动方面存在缺陷。一种四重突变菌株（ugtP pssA mprF ywnE），其细胞膜主要由磷脂酰甘油组成，是可行的，并且以接近野生型的速率生长，尽管它会形成长的、盘绕的细丝。转录组比较确定了在ugtP突变体、pssA mprF ywnE三重突变体和ugtP pssA mprF ywnE四重突变体细胞中表达改变的众多调控子。这些影响包括SigD和FapR调控子的表达普遍下降，以及由sigma(M)和YvrGHb双组分系统介导的细胞包膜应激反应的表达增加。
