Supplementary Material for: <b><i>Francisella </i></b>Is Sensitive to Insect Antimicrobial Peptides

<i>Francisella tularensis</i> causes the zoonotic disease tularemia. Arthropod vectors are important transmission routes for the disease, although it is not known how <i>Francisella</i> survives the efficient arthropod immune response. Here, we used <i>Drosophila melanogaster</i> as a model host for <i>Francisella</i> infections and investigated whether the bacteria are resistant to insect humoral immune responses, in particular to the antimicrobial peptides (AMPs) secreted into the insect hemolymph. Moreover, we asked to what extent such resistance might depend on lipopolysaccharide (LPS) structure and surface characteristics of the bacteria. We analyzed <i>Francisella novicida</i> mutant strains in genes, directly or indirectly involved in specific steps of LPS biosynthesis, for virulence in wild-type and <i>Relish</i>^<i>E20</i> immune-deficient flies, and tested selected mutants for sensitivity to AMPs in vitro. We demonstrate that <i>Francisella</i> is sensitive to specific fly AMPs, i.e. Attacin, Cecropin, Drosocin and Drosomycin. Furthermore, six bacterial genes, <i>kpsF, manB, lpxF, slt, tolA </i>and<i> pal</i>, were found to be required for resistance to <i>Relish</i>-dependent immune responses, illustrating the importance of structural details of <i>Francisella</i> lipid A and Kdo core for interactions with AMPs. Interestingly, a more negative surface charge and lack of O-antigen did not render mutant bacteria more sensitive to cationic AMPs and did not attenuate virulence in flies.

<i>Francisella tularensis</i>（土拉弗朗西斯菌）可引发人畜共患病土拉菌病。节肢动物媒介是该病的重要传播途径，但目前尚不明确<i>Francisella</i>（弗朗西斯菌）如何抵御高效的节肢动物免疫应答。本研究以<i>Drosophila melanogaster</i>（黑腹果蝇）作为<i>Francisella</i>感染的模式宿主，探究该细菌是否对昆虫体液免疫应答具有抗性，尤其是对分泌至昆虫血淋巴中的抗菌肽（antimicrobial peptides，AMPs）的抗性。此外，本研究还探讨了此类抗性在多大程度上依赖于细菌的脂多糖（lipopolysaccharide，LPS）结构与表面特性。我们针对直接或间接参与脂多糖生物合成特定步骤的基因，构建了<i>Francisella novicida</i>（新凶手弗朗西斯菌）突变菌株，检测其在野生型及<i>Relish</i>^<i>E20</i>免疫缺陷果蝇中的毒力，并体外检测了所选突变株对AMPs的敏感性。本研究证实，<i>Francisella</i>对特定果蝇抗菌肽——攻击素（Attacin）、天蚕素（Cecropin）、果蝇素（Drosocin）与果蝇霉素（Drosomycin）——具有敏感性。此外，6个细菌基因<i>kpsF</i>、<i>manB</i>、<i>lpxF</i>、<i>slt</i>、<i>tolA</i>及<i>pal</i>被证实为<i>Francisella</i>抵御<i>Relish</i>依赖型免疫应答所必需，这表明<i>Francisella</i>脂质A与Kdo核心的结构细节在其与AMPs的相互作用中至关重要。值得注意的是，更强的负表面电荷以及O-抗原的缺失并未使突变菌株对阳离子AMPs更为敏感，也未削弱其在果蝇体内的毒力。

搜集汇总

背景与挑战

背景概述

该数据集是《Francisella对昆虫抗菌肽敏感性》研究的补充材料，发布于2012年，聚焦于使用果蝇作为模型宿主，探究Francisella tularensis病原体对昆虫抗菌肽的敏感性及其脂多糖结构在免疫抵抗中的作用。研究发现Francisella对特定昆虫抗菌肽敏感，并识别出六个关键细菌基因与此过程相关，揭示了病原体与昆虫免疫系统交互的分子机制。