DNA analysis of a radiotolerant bacterium Pantoea agglomerans by FT-IR spectroscopy

A radiation tolerance strain, Pantoea agglomerans was isolated from gamma-irradiated carrot samples (Daucus carota). D(10) determination showed that the radioresistance of this bacterium is five-fold higher than Escherichia coli, both belonging to the family of Enterobacteriaceae. DNA isolated from untreated and irradiated bacterial cells was analyzed by FT-IR spectroscopy to investigate the radiotolerance of this bacterium. At doses <5kGy, an alteration of the interbase hydrogen networks was observed and characterized mainly by an increase of bands assigned to the carbonyl non-pairing and the free amine groups. Moderate breakage of the DNA backbone and damage of the osidic structure were also observed. Similar spectral profiles were noticed at doses > or =5kGy, but additional increase of the band intensity of C=C and C=N suggests damages of nucleobases. High number of asymmetric PO(2)(-) and upper shift of symmetric PO(2)(-) are indicative of DNA strand breaks. Osidic damages were evidenced by decrease of the absorption bands ascribed to deoxyribosyl moieties and by appearance of C-OH band. DNA degradation at high irradiation doses was also noticed by electrophoresis using agarose gel. It appeared that DNA underwent covalent cross-linking, as revealed by agglomeration of DNA in the wells of agarose gel.