Université Paris Cité, Institut Cochin , Paris, France.
Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute , Jouy-en-Josas, France.
J Bacteriol. 2023 Oct 26;205(10):e0027423. doi: 10.1128/jb.00274-23. Epub 2023 Oct 9.
Membranes are a universal barrier to all cells. Phospholipids, essential bacterial membrane components, are composed of a polar head and apolar fatty acid (FA) chains. Most bacterial FAs are synthesized by the Type II FA synthesis pathway (FASII). In Streptococcaceae, Enterococci, and , a unique feedback mechanism controls the FASII gene expression. FabT, encoded in the FASII main locus, is the repressor, and it is activated by long-chain acyl-acyl carrier protein (acyl-ACP). Many Streptococci, , but not , possess two ACPs. The AcpA-encoding gene is within the FASII locus and is coregulated with the FASII genes. Acyl-AcpA is the end product of FASII. The AcpB-encoding gene is in operon with encoding an acyl-ACP:phosphate acyltransferase. The role of acyl-AcpB as FabT corepressor is controversial. , which causes a wide variety of diseases ranging from mild non-invasive to severe invasive infections, possesses AcpB. In this study, by comparing the expression of FabT-controlled genes in an -deleted mutant with those in a wild-type and in a mutant strain, grown in the presence or absence of exogenous FAs, we show that AcpB is the FabT main corepressor. Its deletion impacts membrane FA composition and bacterial adhesion to eucaryotic cells, highlighting the importance of FASII control. Membrane composition is crucial for bacterial growth or interaction with the environment. Bacteria synthesize fatty acids (FAs), membrane major constituents, via the Type II FAS (FASII) pathway. Streptococci control the expression of the FASII genes via a transcriptional repressor, FabT, with acyl-acyl carrier proteins (ACPs) as corepressor. that causes a wide variety of diseases ranging from mild non-invasive to severe invasive infections possesses two ACPs. , but not , is a FASII gene. In this study, we show that acyl-AcpBs are FabT main corepressors. Also, AcpB deletion has consequences on the membrane FA composition and bacterial adhesion to host cells. In addition to highlighting the importance of FASII control in the presence of exogeneous FAs for the adaptation of bacteria to their environment, our data indicate that FASII gene repression is mediated by a corepressor whose gene expression is not repressed in the presence of exogenous FAs.
细胞膜是所有细胞的通用屏障。磷脂是细菌膜的重要组成部分，由极性头部和非极性脂肪酸 (FA) 链组成。大多数细菌 FA 是通过 II 型 FA 合成途径 (FASII) 合成的。在链球菌科、肠球菌科和 ，一个独特的反馈机制控制着 FASII 基因的表达。FabT 是 FASII 主基因座编码的阻遏物，它被长链酰基酰基载体蛋白 (acyl-ACP) 激活。许多链球菌、 ，但不是 ，都有两个 ACP。AcpA 编码基因位于 FASII 基因座内，与 FASII 基因共同调控。酰基-AcpA 是 FASII 的终产物。AcpB 编码基因与编码酰基-ACP：磷酸酰基转移酶的 基因成操纵子。酰基-AcpB 作为 FabT 辅助阻遏物的作用存在争议。 ，可引起从轻度非侵入性到严重侵袭性感染等多种疾病，它拥有 AcpB。在这项研究中，通过比较在 缺失突变体中 FabT 控制基因的表达与野生型和 突变体菌株在存在或不存在外源 FA 时的表达，我们表明 AcpB 是 FabT 的主要辅助阻遏物。其缺失会影响膜 FA 组成和细菌对真核细胞的黏附，突出了 FASII 控制的重要性。膜组成对细菌的生长或与环境的相互作用至关重要。细菌通过 II 型 FA 合成 (FASII) 途径合成脂肪酸 (FA)，这是膜的主要成分。链球菌通过转录阻遏物 FabT 控制 FASII 基因的表达，酰基酰基载体蛋白 (ACP) 作为辅助阻遏物。可引起从轻度非侵入性到严重侵袭性感染等多种疾病，它拥有两个 ACP。 ，而不是 ，是 FASII 基因。在这项研究中，我们表明酰基-AcpBs 是 FabT 的主要辅助阻遏物。此外，AcpB 缺失会影响膜 FA 组成和细菌对宿主细胞的黏附。除了突出外源 FA 存在时 FASII 控制对细菌适应环境的重要性外，我们的数据还表明，FASII 基因的抑制是由一种辅助阻遏物介导的，而该辅助阻遏物的基因表达在外源 FA 存在时不受抑制。
