Action Spectra Studies of Phycocyanin Formation in a Mutant of Cyanidium caldarium

Abstract

1. A chlorophyll-less mutant of Cyanidium caldarium was used to determine the action spectrum of phycocyanin formation. 2. The action spectrum for phycocyanin formation by young cells of the chlorophyll-less mutant (GGB) has maxima at 420 mμ and 550-600 mμ; this suggests that the primary photoreceptor (or precursor) may be an unidentified heme compound. 3. Evidence indicates that the hemelike compound proposed as a photoreceptor (or precursor) in young cells undergoes conversion in older cells to an unidentified form more strongly activated by light of longer wavelengths (550-650 mμ). 4. Conversion of the primary photoreceptor (or precursor) is promoted in older cells by pre-illumination in blue light (420 mμ). 5. The requirement of light in the reactions leading to the synthesis of phycocyanin can be eliminated by providing an unidentified factor(s) contained in some culture-media components.