Department of Infectious Diseases, College of Veterinary Medicine, University of Georgiagrid.213876.9, Athens Georgia, USA.
Department of Microbiology, College of Arts and Sciences, University of Georgiagrid.213876.9, Athens Georgia, USA.
J Bacteriol. 2022 Feb 15;204(2):e0049821. doi: 10.1128/JB.00498-21. Epub 2021 Nov 29.
Gram-negative bacteria utilize glycerophospholipids (GPLs) as phospho-form donors to modify various surface structures. These modifications play important roles in bacterial fitness in diverse environments influencing cell motility, recognition by the host during infection, and antimicrobial resistance. A well-known example is the modification of the lipid A component of lipopolysaccharide by the phosphoethanolamine (pEtN) transferase EptA that utilizes phosphatidyethanoalmine (PE) as the phospho-form donor. Addition of pEtN to lipid A promotes resistance to cationic antimicrobial peptides (CAMPs), including the polymyxin antibiotics like colistin. A consequence of pEtN modification is the production of diacylglycerol (DAG) that must be recycled back into GPL synthesis via the diacylglycerol kinase A (DgkA). DgkA phosphorylates DAG forming phosphatidic acid, the precursor for GPL synthesis. Here we report that deletion of in polymyxin-resistant E. coli results in a severe reduction of pEtN modification and loss of antibiotic resistance. We demonstrate that inhibition of EptA is regulated posttranscriptionally and is not due to EptA degradation during DAG accumulation. We also show that the inhibition of lipid A modification by DAG is a conserved feature of different Gram-negative pEtN transferases. Altogether, our data suggests that inhibition of EptA activity during DAG accumulation likely prevents disruption of GPL synthesis helping to maintain cell envelope homeostasis. For Gram-negative bacteria, modification of a key surface structure known as lipopolysaccharide (LPS) is critical for resistance to cationic antimicrobial peptides, including the last-resort antibiotic polymyxin. One key enzyme that is critical for resistance is EptA that adds a positively charged residue to LPS, preventing polymyxin binding. Here we show that EptA can be posttranscriptionally regulated by a key cell envelope lipid leading to changes in antibiotic resistance.
革兰氏阴性菌利用甘油磷脂 (GPLs) 作为磷酸基供体来修饰各种表面结构。这些修饰在影响细胞运动性、感染期间被宿主识别以及抗微生物药物耐药性的不同环境中的细菌适应性中起着重要作用。一个众所周知的例子是脂多糖 (LPS) 的脂质 A 组分被磷酸乙醇胺 (pEtN) 转移酶 EptA 修饰，该酶利用磷脂酰乙醇胺 (PE) 作为磷酸基供体。脂质 A 中 pEtN 的添加促进了对阳离子抗菌肽 (CAMP) 的耐药性，包括多粘菌素类抗生素如粘菌素。pEtN 修饰的结果是产生二酰基甘油 (DAG)，必须通过二酰基甘油激酶 A (DgkA) 回收到 GPL 合成中。DgkA 使 DAG 磷酸化形成磷脂酸，这是 GPL 合成的前体。在这里，我们报告说，多粘菌素耐药的大肠杆菌中缺失会导致 pEtN 修饰严重减少和抗生素耐药性丧失。我们证明 EptA 的抑制是转录后调节的，并且不是由于 DAG 积累期间 EptA 降解引起的。我们还表明，DAG 对脂质 A 修饰的抑制是不同革兰氏阴性 pEtN 转移酶的保守特征。总之，我们的数据表明，在 DAG 积累期间抑制 EptA 活性可能有助于防止 GPL 合成中断，有助于维持细胞包膜的稳态。对于革兰氏阴性菌来说，对一种称为脂多糖 (LPS) 的关键表面结构的修饰对于抵抗阳离子抗菌肽至关重要，包括最后一道抗生素多粘菌素。一种关键的酶 EptA 对于耐药性至关重要，它在 LPS 上添加一个带正电荷的残基，防止多粘菌素结合。在这里，我们表明 EptA 可以通过关键的细胞包膜脂质进行转录后调节，导致抗生素耐药性的变化。
