Role of carotenoid pigments in radio-resistant micrococci

Abstract

The carotenoid pigments of two radio-resistant bacteria viz., Micrococci radiophilus and Micrococcus radiodurans, were affected qualitatively by culturing them in the presence of nicotine, and quantitatively by culturing them in the presence of diphenylamine or at extreme pH levels. Alteration of the pigment content of these organisms, either qualitatively or quantitatively, had no effect on their sensitivity to gamma irradiation.Cells of these radio-resistant micrococci, which normally contained predominantly keto-carotenoids, were found to accumulate the acyclic carotenoid lycopene when grown in the presence of nicotine. Pigments of nicotine-grown cells were stable to 3.0 Mrad as compared with those of either DPA-grown or normal cells which were totally destroyed at 1.0 Mrad.