Photosynthetic adaptation and multicellularity in the Antarctic psychrophile, Chlamydomonas priscuii

Acclimation, adaptation and survival in persistent cold polar environments are complex phenomena associated with myriad molecular, biochemical and physiological mechanisms. The psychrophile, Chlamydomonas priscuii, is endemic to Lake Bonney, Antarctica. Adaptation to its extreme polar environment includes homeoviscous adaptation of membranes, maintenance of energy balance through photostasis and surface area to volume ratio. In addition to these mechanisms, this psychrophile can exist in culture as motile, single cells or as immobile, multicellular palmelloids. Comparative biochemical, physiological, microscopic and spectroscopic analyses of purified single cells and palmelloids indicate that the conversion of single cells to multicellular palmelloids alters the composition and organization of the photosynthetic apparatus. This enhances photoprotection of the photosynthetic apparatus from light and low temperature stress by minimizing potential cellular energy im-balances and safely dissipating excessive excitation energy by nonphotochemical quenching mechanisms. In addition to decreased susceptibility to predation, enhanced photoprotection from photoinhibition associated with palmelloid formation may be a complementary, selective, evolutionary advantage for the induction of multicellularity in green algae.