Growth and Photosynthesis of Nanochlorum eucaryotum, a New and Extremely Small Eucaryotic Green Alga

Nanochlorum eucaryotum is a very small species of unicellular coccoid green algae (1.5 nm). The growth of Nanochlorum under different conditions of salinity, pH and light intensities was studied. Optimal growth rates were observed with normal sea water salinity and low light conditions at pH 7.0. The contents of chlorophylls, carotinoids, soluble proteins and the chlorophyll a to chlorophyll b ratio were measured. The light saturating curves of Nanochlorum cells grown under light intensities of 100 lx, 2000 lx and 10000 lx reveal a very narrow capacity of light adaptation. When cultured under higher light intensities, Nanochlorum was not able to reach high photosynthetic activities but underwent a photoinhibition of photosynthesis. The contents of cytochrome f, P-700 and ribulosebisphosphate carboxylase were low and comparable with those of low light adapted Chlorella cells. The analysis of the chlorophyll-protein complexes shows that about 80% of total chlorophyll is bound in the light harvesting chlorophyll protein complexes. All results indicate that Nanochlorum is a low light adapted marine organism with very narrow ecological flexibility.