1H NMR as a Tool for Monitoring Extracellular Medium Evolution in Microbial Cultures

Xylella fastidiosa is a slow-growing and nutritionally demanding bacterium, making robust analytical workflows essential for investigating its extracellular metabolic activity under in vitro conditions. In this work, 1H NMR spectroscopy was applied as a non-destructive tool to monitor the temporal evolution of bacterial culture supernatants grown in two media with different chemical complexity: XFM, a defined minimal medium, and PD3, a richer cultivation medium.[1] Supernatants were collected at five time points, centrifuged to remove cells, aliquoted, and stored at -80 °C until analysis. Sample preparation and acquisition conditions were optimized to obtain reproducible 1D 1H NMR spectra from complex extracellular matrices. Different pulse sequences were compared, and CPMG provided better baseline quality and signal resolution than NOESY, especially in samples containing proteinaceous components. The optimized workflow revealed clear time-dependent spectral changes in both media and confirmed the suitability of 1H NMR for monitoring extracellular medium evolution in slow-growing microbial systems. This approach provides a practical methodological basis for future exometabolomic and footprinting applications.[2]