Abstract
The radical attack of ascorbic acid was investigated by Fourier transform infrared spectroscopy. This physico-chemical technique was used as a convenient and easy-to-run method to monitor radical-induced damage on three bacterial strains previously included in the Micrococcaceae family. Increasing concentrations of ascorbic acid were added to the culture media during the stationary phase. As soon as the antioxidant defenses of the bacteria were overwhelmed, striking changes occurred in the infrared spectra, especially in the 1700–900 cm−1 region, which is spectroscopically assigned to the amide I and II components of proteins, nucleotide bases, phosphodiester backbone, and sugar rings. These changes were correlated with the oxidant effect of ascorbic acid, but the response to free radicals generated was dependent on the strains. Micrococcus luteus and Kocuria rosea were sensitive to the lowest ascorbic acid concentrations, while a concentration beyond 10 mM was necessary to cause damage to biomolecular components of the radioresistant Deinococcus radiodurans. Thus, Fourier transform infrared analysis allowed a rapid investigation of the metabolic changes caused by radical attack, and the spectral alterations could be correlated with biochemical and phenotypical data.
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