We report the successful inactivation of P. aeruginosa strain by femtosecond infrared (IR) laser radiation at the resonant wavelengths of 3.15 μm and 6.04 μm, chosen due to the presence of characteristic molecular vibrations in the main structural elements of the bacterial cells in these spectral ranges: vibrations of amide groups in proteins (1500-1700 cm-1), and C-H vibrations in membrane proteins and lipids (2800-3000 cm-1). The underlying bactericidal structural molecular changes were revealed by the stationary Fourier-transform IR spectroscopy, with the spectral peaks parameters being obtained by Lorentzian fitting with the hidden peaks revealed by the second derivative calculations, while no visible damage to the cell membranes was identified by scanning and transmission electron microscopy.
Keywords: Fourier-transform IR spectroscopy; IR laser inactivation; bacteria.