<i>p</i>‑Cresol and <i>C. difficile</i>: A Love-Hate StoryRevealed by Raman Spectroscopy

<i>Clostridioides difficile</i> is known to produce <i>p</i>-cresol, a phenolic compound with selective antimicrobial properties, which may contribute to its competitive advantage within the gut microbiome. In this study, we investigated the interaction between <i>Clostrioides difficile</i> and <i>Escherichia coli</i> in coculture to assess the role of <i>p</i>-cresol in modulating interspecies dynamics. Raman spectroscopy was employed as a label-free, nondestructive analytical technique to profile the molecular signatures of both species in mono- and coculture. Excitation wavelengths at 244 and 532 nm were used to enhance complementary vibrational features, including those associated with aromatic compounds like <i>p</i>-cresol. Our results demonstrate distinct spectral changes in coculture conditions suggesting the involvement of <i>p</i>-cresol and its impact on the biochemical composition of <i>E. coli</i>. This dual-wavelength Raman approach offers a powerful means of characterizing microbial interactions and identifying metabolic markers that may drive microbial competition and survival.