Staphylococcus epidermidis has long been known as a major bacterial coloniser of the human skin, yet it is also a prominent nosocomial pathogen. Its remarkable ability to assemble structured biofilms has been its major known pathogenic feature to date. Notwithstanding important discoveries that have been accomplished, several questions about S. epidermidis biofilm formation still remain to be elucidated. This study aimed to assess whether iron availability modulates S. epidermidis biofilm formation and, if so, to explore how such modulation occurs. Biofilms of three S. epidermidis strains were grown under iron-enriched/-deficient conditions and several physiologic and transcriptomic changes were assessed. Our data revealed that while physiologic iron levels do not compromise biofilm formation, iron excess or deficiency is detrimental for this process. Conversely, biofilm cells were not affected in the same way when grown planktonically. By studying biofilm cells in detail we found that their viability and cultivability were seriously compromised by iron deficiency. Also, a temporal analysis of biofilm formation revealed that iron excess/deficiency: i) impaired biomass accumulation from 6h onwards, and ii) induced changes in the biofilm structure, indicating that iron availability plays a pivotal role from an early biofilm development stage. The expression of several putative iron-related genes, namely encoding siderophore biosynthesis/transport-related proteins, was found to be modulated by iron availability, providing a biological validation of their function on S. epidermidis iron metabolism. This study therefore provides evidence that iron plays a pivotal role on S. epidermidis biofilm formation.

中文翻译：

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表皮葡萄球菌在很大程度上取决于铁的可用性以形成生物膜。

表皮葡萄球菌长期以来一直被认为是人类皮肤的主要细菌定居者，但它也是一种突出的医院病原体。迄今为止，其组装结构化生物膜的卓越能力一直是其主要的已知致病特征。尽管已经完成了重要的发现，但是关于表皮葡萄球菌生物膜形成的几个问题仍然有待阐明。这项研究旨在评估铁的可用性是否能调节表皮葡萄球菌的生物膜形成，如果是，则探讨这种调节是如何发生的。在富铁/缺乏铁的条件下生长了三种表皮葡萄球菌菌株的生物膜，并评估了一些生理和转录组变化。我们的数据显示，虽然生理性铁水平不会损害生物膜的形成，铁过量或不足对这个过程是有害的。相反，浮游生长时，生物膜细胞不会以相同的方式受到影响。通过详细研究生物膜细胞，我们发现铁缺乏严重损害了它们的生存能力和可培养性。此外，对生物膜形成的时间分析还显示出铁的过量/缺乏：i）从6h开始损害了生物量的积累，ii）诱导了生物膜结构的变化，表明铁的可用性从早期生物膜发展阶段起着举足轻重的作用。发现若干假定的铁相关基因的表达，即编码铁载体生物合成/运输相关蛋白，其表达受到铁可用性的调节，从而提供了其对表皮葡萄球菌铁代谢功能的生物学验证。