Complementary Chromatic Adaptation in the Red Alga Galdieria yellowstonensis

Galdieria yellowstonensis, an extremophilic red alga, contains pigments from both cyanobacterial and eukaryotic origins. Chromatic adaptation under white, red, and blue light revealed differences in exciton and electron usage. Blue light induced a threefold stronger electrochromic shift and sixfold higher Photosystem I (PSI) oxidation than red light. Cytochromes b and f were half as oxidized under limited light wavelengths. Red light reduced active QB sites of Photosystem II (PSII) threefold but maintained electron flux to cytochrome b6f and PSI. Blue light culture exhibits high PSI-cyclic electron flow, generating a strong proton gradient, while PSII remains highly efficient in electron removal.