THE RELATIONSHIP BETWEEN CAROTENOID PIGMENTS AND RESISTANCE TO RADIATION IN NON‐PHOTOSYNTHETIC BACTERIA

Abstract

Abstract— A radiation‐resistant Micrococcus sp. and a colorless mutant subject to gamma radiation were found to have identical killing curves. Similar results were obtained with ultraviolet light. However when exposed to visible light in the presence of the photosensitizer, toluidine blue, the pigmented wild‐type was unaffected whereas the colorless mutant was killed. Sarcina lutea and a colorless mutant were killed at similar rates following exposure to x‐rays and U.V. light, whereas previous studies have demonstrated that the pigmented wild‐type is protected against lethal photosensitizations by visible light. It is concluded that the effect of carotenoid pigments in radiation damage is limited to protecting cells against the lethal effects of visible light and is without effect at shorter wavelengths.