Effect of Radical Attack on Bacteria: An Application of FT-IR Spectroscopy

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.

Fourier transform IR spectroscopic appraisal of radiation damage in Micrococcus luteus

“…38 The carbohydrate composition of this micrococcal lipoglycan was examined following acid hydrolysis of crude extracts, 39 and mannose was found to be the major component of the hydrolysates. Consequently, the slight changes in intensity and shape observed in spectra 4 and 5 at 1060 cm Ϫ1 that we attributed to mannose 25 might arise from a modified composition of the cell wall during the reincubation phase.…”

“…A strict experimental protocol concerning the medium, incubation time, temperature, bacterial harvest, and sample preparation was first established. M. luteus was grown under aerobic conditions 25 in a shaking water bath at 33°C for 24 h in order to obtain a stationary phase. Briefly, the medium contained the following: 5 g of bactotryptone (Difco), 1 g of yeast extract (Difco), and 1 g of glucose per liter of distilled water.…”

Analysis and Monitoring of Oxidative Stress in Exercise and Training by FTIR Spectrometry

“…Cellular changes due to reactive oxygen species have been observed on proteins, nucleotide bases, phosphodiester backbone, and sugar ring vibrations. 32,33 For erythrocytes, the phospholipid bilayer has been extensively studied by IR spectrometry 19,34,35 notably the fatty acid chain saturation degree. 36 As shown in Figure 2, the main erythrocyte IR absorptions can be easily interpreted: fatty acyl moieties of erythrocytes stem exclusively from phospholipids; hemoglobin (Hb) accounts for about 80% of erythrocyte proteins, spectrin for about 10%, and there is no nucleus within this cell; over membrane glycoprotein species, only lactic acid and possibly glucose for patients with diabetes are present within the cell (Table 1).…”

Study of energetic-particle-irradiation induced biological effect on Rhizopus oryzae through synchrotron-FTIR micro-spectroscopy

“…The maximum of amide I peak at 1635 cm À1 is attributed to the C@O stretching and CAN bending vibrational modes, and the maximum of amide II peak at 1535 cm À1 is assigned to the NAH bending and CAN stretching ones. The intensity ratio of the IR band at 1635 cm À1 to the 1535 cm À1 band was used as a marker of protein conformational changes [39,40]. The change of protein secondary structure from a-helix to b-sheet is often associated with the decrease of the absorbance at 1645 cm À1 , and so it also corresponds to the decrease of this ratio [37].…”