Université de Paris, Institut Cochingrid.462098.1, INSERM, CNRS, Paris, France.
Centre National de Référence des Streptocoques, Paris, France.
J Bacteriol. 2021 Sep 23;203(20):e0022121. doi: 10.1128/JB.00221-21. Epub 2021 Jul 26.
Enterococcus faecalis, a multiple antibiotic-resistant Gram-positive bacterium, has emerged as a serious nosocomial pathogen. Here, we used a genetic approach to characterize the strategies used by E. faecalis to fulfill its requirements for endogenous fatty acid (FA) synthesis and . The type II fatty acid synthesis (FASII) pathway is encoded by two operons and two monocistronic genes. Expression of all of these genes is repressed by exogenous FAs, which are incorporated into the E. faecalis membrane and modify its composition. Deletion of nine genes of the 12-gene operon abolished growth in an FA-free medium. Addition of serum, which is lipid rich, restored growth. Interestingly, the E. faecalis membrane contains cyclic fatty acids that modify membrane properties but that are unavailable in host serum. The gene that encodes the cyclopropanation process is located in a locus independent of the FASII genes. Its deletion did not alter growth under the conditions tested, but yielded bacteria devoid of cyclic FAs. No differences were observed between mice infected with wild-type (WT) or with FASII or cyclopropanation mutant strains, in terms of bacterial loads in blood, liver, spleen, or kidneys. We conclude that in E. faecalis, neither FASII nor cyclopropanation enzymes are suitable antibiotic targets. Membrane lipid homeostasis is crucial for bacterial physiology, adaptation, and virulence. Fatty acids are constituents of the phospholipids that are essential membrane components. Most bacteria incorporate exogenous fatty acids into their membranes. Enterococcus faecalis has emerged as a serious nosocomial pathogen that is responsible for urinary tract infections, bacteremia, and endocarditis and is intrinsically resistant to numerous antibiotics. E. faecalis synthesizes saturated and unsaturated fatty acids, as well as cyclic fatty acids that are not found in the human host. Here, we characterized mutant strains deficient in fatty acid synthesis and modification using genetic, biochemical, and approaches. We conclude that neither the fatty acid synthesis pathway nor the cyclopropanation enzyme are suitable targets for E. faecalis antibiotic development.
屎肠球菌是一种多重抗生素耐药的革兰氏阳性菌，已成为严重的医院获得性病原体。在这里，我们使用遗传方法来描述屎肠球菌满足其内源脂肪酸（FA）合成和的策略。II 型脂肪酸合成（FASII）途径由两个操纵子和两个单顺反子基因编码。所有这些基因的表达都受到外源性 FA 的抑制，外源性 FA 被掺入屎肠球菌的膜中并改变其组成。12 基因操纵子的 9 个基因缺失导致在无 FA 培养基中生长受阻。添加富含脂质的血清可恢复生长。有趣的是，屎肠球菌膜中含有可改变膜性质但宿主血清中不存在的环状脂肪酸。编码环丙烷化过程的 基因位于与 FASII 基因无关的基因座上。在测试的条件下，其缺失不会改变生长，但产生缺乏环状 FAs 的细菌。在感染野生型（WT）或 FASII 或环丙烷化突变株的小鼠中，血液、肝脏、脾脏或肾脏中的细菌负荷没有观察到差异。我们得出的结论是，在屎肠球菌中，FASII 或环丙烷化酶都不是合适的抗生素靶标。膜脂质稳态对于细菌生理学、适应和毒力至关重要。脂肪酸是磷脂的组成部分，磷脂是必不可少的膜成分。大多数细菌将外源性脂肪酸掺入其膜中。屎肠球菌已成为一种严重的医院获得性病原体，可引起尿路感染、菌血症和心内膜炎，并且对多种抗生素具有固有耐药性。屎肠球菌合成饱和和不饱和脂肪酸以及在人类宿主中不存在的环状脂肪酸。在这里，我们使用遗传、生化和生物化学方法表征了脂肪酸合成和修饰缺陷的突变株。我们得出的结论是，脂肪酸合成途径和环丙烷化酶都不是屎肠球菌抗生素开发的合适靶标。
