Inactivation of Neurospora crassa conidia by singlet molecular oxygen generated by a photosensitized reaction

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Abstract
Photodynamic damage of N. crassa conidia was studied in the presence of the photosensitizing dye, toluidine blue O. Conidia which germinated to form colonies decreased in number as irradiation time became longer. The photoinactivation of conidia was suppressed by azide, bovine serum albumin and histidine and was stimulated in deuterium oxide. Wild-type conidia were less sensitive to the irradiation than albino conidia. In the wild type, carotenoid-enriched conidia were more resistant to the lethal damage than the conidia containing small amounts of carotenoids. Apparently singlet molecular O causes photodynamic lethal damage to N. crassa conidia and singlet molecular O is quenched by endogenous carotenoids.