Radical induced damage of Micrococcus luteus bacteria monitored using FT‒IR spectroscopy

Abstract

Oxidative damage induced by ascorbic acid (AA) and hydrogen peroxide (H₂O₂) was monitored by Fourier transform infrared spectroscopy (FT‒IR); it appeared as a rapid and convenient means to follow the biochemical changes generated in the culture media of the yellow-pigmented Micrococcus luteus. Beyond a threshold of 20 mM for AA and of 40 mM for H₂O₂ (final concentration), antioxidant systems were overwhelmed and significant changes were observed in the bacterial spectra, particularly in the 1430–900 cm⁻¹ region; this spectral window provided large information about carboxylate groups, phosphate-carrying compounds and polysaccharides implicated in the radical process. The spectroscopic results indicated that for the same final concentration, the toxicity of H₂O₂ was less important than that of AA toward M. luteus cells, although H₂O₂ had a more damaging effect on proteins. Thus, FT-IR spectroscopy was an appropriate physico-chemical tool suitable in biochemical and clinical research for early characterization of any type of radical aggression, and for rapid detection of the damage intensity.