SENSITIVITY OF THE ELECTRON TRANSPORT CHAIN OF PIGMENTED AND NON‐PIGMENTED SARCINA MEMBRANES TO PHOTODYNAMIC ACTION

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Abstract
Abstract— With malate as substrate, the respiratory system of Sarcina lutea is subject to photodynamic action when toluidine blue is added as a photosensitiser. Both whole cells and isolated cell membranes show similar photoinactivation. Cell and membrane suspensions of a carotenoid‐containing strain are significantly less sensitive than those from a non‐pigmented mutant prepared from the pigmented strain. Addition of histidine also provides photoprotection. Attempts to locate the site of photoinactivation within the respiratory system lead to the conclusion that several sites are affected. Short periods of illumination do not result in permanent damage since activity is recovered in these suspensions when incubated in the dark subsequent to illumination. The significance of these results and the possible mechanisms involved are discussed.