Université de Caen Normandie, EA4655 U2RM (équipe «Antibio-résistance»), CHU de Caen, Caen, France.
Université de Caen Normandie, GRAM 2.0, CHU de Caen, Service de Microbiologie, Caen, France.
BMC Microbiol. 2020 Oct 28;20(1):328. doi: 10.1186/s12866-020-02016-x.
Staphylococcus lugdunensis is a coagulase-negative Staphylococcus part of the commensal skin flora but emerge as an important opportunistic pathogen. Because iron limitation is a crucial stress during infectious process, we performed phenotypic study and compared proteomic profiles of this species incubated in absence and in presence of the iron chelator 2,2'-dipyridyl (DIP).
No modification of cell morphology nor cell wall thickness were observed in presence of DIP. However iron-limitation condition promoted biofilm formation and reduced the ability to cope with oxidative stress (1 mM HO). In addition, S. lugdunensis N920143 cultured with DIP was significantly less virulent in the larvae of Galleria mellonella model of infection than that grown under standard conditions. We verified that these phenotypes were due to an iron limitation by complementation experiments with FeSO. By mass spectrometry after trypsin digestion, we characterized the first iron-limitation stress proteome in S. lugdunensis. Among 1426 proteins identified, 349 polypeptides were differentially expressed. 222 were more and 127 less abundant in S. lugdunensis incubated in iron-limitation condition, and by RT-qPCR, some of the corresponding genes have been shown to be transcriptionally regulated. Our data revealed that proteins involved in iron metabolism and carriers were over-expressed, as well as several ABC transporters and polypeptides linked to cell wall metabolism. Conversely, enzymes playing a role in the oxidative stress response (especially catalase) were repressed.
This phenotypic and global proteomic study allowed characterization of the response of S. lugdunensis to iron-limitation. We showed that iron-limitation promoted biofilm formation, but decrease the oxidative stress resistance that may, at least in part, explained the reduced virulence of S. lugdunensis observed under low iron condition.
凝固酶阴性葡萄球菌（Staphylococcus lugdunensis）是一种共生皮肤菌群中的葡萄球菌，但也是一种重要的机会致病菌。由于铁限制是感染过程中的一个关键应激因素，我们进行了表型研究，并比较了在缺乏和存在铁螯合剂 2,2'-联吡啶（DIP）的情况下该物种的蛋白质组图谱。
在 DIP 存在的情况下，细胞形态或细胞壁厚度没有发生变化。然而，铁限制条件促进了生物膜的形成，并降低了应对氧化应激（1mM HO）的能力。此外，在感染幼虫模型中，与在标准条件下生长相比，用 DIP 培养的 S. lugdunensis N920143 的毒力显著降低。我们通过用 FeSO 进行互补实验验证了这些表型是由于铁限制引起的。通过胰蛋白酶消化后的质谱分析，我们鉴定了 S. lugdunensis 中第一个铁限制应激蛋白质组。在鉴定的 1426 种蛋白质中，有 349 种多肽表达水平不同。在铁限制条件下培养的 S. lugdunensis 中，222 种多肽表达增加，127 种多肽表达减少，通过 RT-qPCR 显示，一些相应的基因转录受到调控。我们的数据表明，铁代谢和载体相关的蛋白以及几个 ABC 转运蛋白和与细胞壁代谢相关的多肽被过度表达。相反，参与氧化应激反应的酶（特别是过氧化氢酶）被抑制。
这项表型和全蛋白质组研究有助于描述 S. lugdunensis 对铁限制的反应。我们表明，铁限制促进了生物膜的形成，但降低了氧化应激的抵抗力，这至少部分解释了在低铁条件下观察到的 S. lugdunensis 毒力降低的现象。
