Antimicrobial peptides (AMPs) are currently known for their potential as an alternative to conventional antibiotics and new weapons against drug-resistant bacteria and biofilms. In the present work, the mechanism of action of a cyclic (colistin) and a linear (catestatin) AMP on a young E. coli biofilm was deciphered from the molecular to the cellular scale. To this end, infrared spectroscopy (attenuated total reflection–Fourier transform infrared) assisted by chemometric analysis was combined with fluorescence and atomic force microscopies to address the very different behaviors of both AMPs. Indeed, the colistin dramatically damaged the bacterial cell wall and the metabolism even though its action was not homogeneous over the whole bacterial population and repopulation can be observed after peptide removal. Conversely, catestatin did not lead to major damages in the bacterial morphology but its action was homogeneous over the whole bacterial population and the cells were unable to regrow after the peptide treatment. Our results strongly suggested that contrary to the cyclic molecule, the linear one is able to cause irreversible damages in the bacterial membrane concomitantly to a strong impact on the bacterial metabolism.

中文翻译：

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循环和线性抗菌肽作用对年轻生物膜的光谱化学和纳米力学指纹之间的差异。

目前，抗菌肽（AMP）可以替代常规抗生素和对抗耐药菌和生物膜的新型武器，因此具有潜在的优势。在目前的工作中，环状（colistin）和线性（catestatin）AMP对年轻大肠杆菌的作用机理生物膜从分子尺度到细胞尺度被破译。为此，结合化学计量学分析的红外光谱（衰减全反射-傅立叶变换红外）与荧光和原子力显微镜相结合，以解决两种AMPs截然不同的行为。实际上，大肠菌素即使在整个细菌种群中作用不均一，也能严重破坏细菌细胞壁和代谢，并且在去除肽后可以观察到种群重新聚集。相反，Catestatin不会导致细菌形态的重大损害，但其作用在整个细菌群体中是均一的，在肽处理后细胞无法再生。我们的结果强烈表明，与环状分子相反，