Large-scale domain movement in the cytochrome bc1 complex

Abstract

Phytoplankton in the Southern Ocean has to deal with deep mixing through the water column, due to prevailing weather conditions of almost continuous strong winds. Acclimation to rapid changes in irradiance levels requires flexibility of the photosystems. Two common Antarctic microalgae were tested for their ability of photoacclimation. A diatom, Chaetoceros brevis, and a flagellate, Pyramimonas sp., were subjected to a variable light climate simulating vertical mixing. Photosynthetic responses were recorded by means of dual-modulated fluorescence techniques, besides analyses of pigment composition and in vivo absorption spectra. The two algal groups showed distinct means of photoacclimation. Pyramimonas readily responded to changes in irradiance by downregulation of photosynthetic activity at moments of high irradiance. C. brevis showed to be less flexible in photosynthetic performance; the diatom apparantly acclimated to an average amount of light received. These different strategies of photoacclimation can be related to structural differences in the photosynthetic apparatus.