Raman spectroscopy in cell biology and microbiology

The Raman spectrum of living cells and microorganisms contains highly specific fingerprint-like signatures, useful in unequivocally identifying different species and interpreting physiological and metabolic responses to environmental stressors. In situ Raman imaging with dedicated highly sensitive instruments can translate selected spectroscopic fingerprints into vivid snapshots of molecular species or specific physiological reactions. Time-lapse experiments, crucial in characterizing growth-dependent phenomena and metabolic response to drugs or substrates, are possible because Raman imaging is life compatible. This review covers miscellaneous examples of Raman analyses and imaging of eukaryotic cells, bacteria, and viruses. Fundamental microbiological analyses covered here include (i) identification of different species of cells, bacteria, and viruses; (ii) characterization of the metabolic responses of cells and bacteria to different substrates; (iii) time-lapse analyses of cell metabolic reactions upon viral inoculation; (iv) chemical imaging of axon sprouting in neuronal cells; and (v) visualization of the myelinating activity of living Schwann cells in coculture with neuronal cells. The spectroscopic findings displayed here, which are based on a machine learning approach applied to Raman analysis and imaging, demonstrate the invaluable potential for Raman spectroscopy in biophysics research.