XVI International Botanical Congess

Unicellular green algae that were traditionally assigned to the genus Chlorella Beijerinck, were characterized by different methods to resolve their phylogenetic relationships within the Chlorophyta. Biochemical, physiological, ultrastructural, and molecular data were compared with an 18S rRNA phylogeny. The molecular tree shows that only C. vulgaris, C. lobophora, C. sorokiniana, and C. kessleri should be kept in the genus Chlorella. Common characteristics of these species are glucosamine as a predominant cell wall component and presence of a double thylakoid bisecting the pyrenoid matrix. Norspermine, norspermidine, and secondary carotenoids are never produced. Other AChlorella@ species belong to different taxa within the Trebouxiophyceae and the Chlorophyceae. The latter ones can easily be recognized by the production of secondary carotenoids under nitrogen-deficient conditions.