Pandin Caroline, Caroff Martine, Condemine Guy
Université Lyon, INSA de Lyon, CNRS UMR5240 Microbiologie Adaptation et Pathogénie, Villeurbanne, France.
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Orsay, France LPS-BioSciences, Université de Paris-Sud, Orsay, France.
Appl Environ Microbiol. 2016 Oct 14;82(21):6423-6430. doi: 10.1128/AEM.01757-16. Print 2016 Nov 1.
Modification of teichoic acid through the incorporation of d-alanine confers resistance in Gram-positive bacteria to antimicrobial peptides (AMPs). This process involves the products of the dltXABCD genes. These genes are widespread in Gram-positive bacteria, and they are also found in a few Gram-negative bacteria. Notably, these genes are present in all soft-rot enterobacteria (Pectobacterium and Dickeya) whose dltDXBAC operons have been sequenced. We studied the function and regulation of these genes in Dickeya dadantii dltB expression was induced in the presence of the AMP polymyxin. It was not regulated by PhoP, which controls the expression of some genes involved in AMP resistance, but was regulated by ArcA, which has been identified as an activator of genes involved in AMP resistance. However, arcA was not the regulator responsible for polymyxin induction of these genes in this bacterium, which underlines the complexity of the mechanisms controlling AMP resistance in D. dadantii Two other genes involved in resistance to AMPs have also been characterized, phoS and phoH dltB, phoS, phoH, and arcA but not dltD mutants were more sensitive to polymyxin than the wild-type strain. Decreased fitness of the dltB, phoS, and phoH mutants in chicory leaves indicates that their products are important for resistance to plant AMPs.
Gram-negative bacteria can modify their lipopolysaccharides (LPSs) to resist antimicrobial peptides (AMPs). Soft-rot enterobacteria (Dickeya and Pectobacterium spp.) possess homologues of the dlt genes in their genomes which, in Gram-positive bacteria, are involved in resistance to AMPs. In this study, we show that these genes confer resistance to AMPs, probably by modifying LPSs, and that they are required for the fitness of the bacteria during plant infection. Two other new genes involved in resistance were also analyzed. These results show that bacterial resistance to AMPs can occur in bacteria through many different mechanisms that need to be characterized.
通过掺入D - 丙氨酸对磷壁酸进行修饰可使革兰氏阳性菌对抗菌肽（AMP）产生抗性。这一过程涉及dltXABCD基因的产物。这些基因在革兰氏阳性菌中广泛存在，在少数革兰氏阴性菌中也有发现。值得注意的是，所有软腐肠杆菌（果胶杆菌属和迪基氏菌属）中都存在这些基因，其dltDXBAC操纵子已被测序。我们研究了迪基氏菌中这些基因的功能和调控。在AMP多粘菌素存在的情况下，迪基氏dadantii中的dltB表达被诱导。它不受控制一些参与AMP抗性基因表达的PhoP调控，而是受已被鉴定为参与AMP抗性基因激活剂的ArcA调控。然而，arcA并不是该细菌中多粘菌素诱导这些基因的调控因子，这凸显了控制迪基氏dadantii中AMP抗性机制的复杂性。另外两个参与AMP抗性的基因也已被鉴定，即phoS和phoH。dltB、phoS、phoH和arcA突变体，但不是dltD突变体，比野生型菌株对多粘菌素更敏感。dltB、phoS和phoH突变体在菊苣叶中的适应性降低表明它们的产物对于抵抗植物AMP很重要。
革兰氏阴性菌可修饰其脂多糖（LPS）以抵抗抗菌肽（AMP）。软腐肠杆菌（迪基氏菌属和果胶杆菌属）在其基因组中拥有dlt基因的同源物，在革兰氏阳性菌中，这些基因参与对AMP的抗性。在本研究中，我们表明这些基因可能通过修饰LPS赋予对AMP的抗性，并且它们是植物感染期间细菌适应性所必需的。还分析了另外两个参与抗性的新基因。这些结果表明细菌对AMP的抗性可通过许多不同机制发生，这些机制需要被表征。
