• chemotaxonomy;
  • Chlorella-like” species;
  • Chlorella vulgaris;
  • ergosterol;
  • Trebouxiophyceae

Chlorella is one of the best-studied green microalgal genera because of its wide use as a model system and its utilization in biotechnology. Since the description of the type species Chlorella vulgaris Beij., more than a hundred species have been established in the literature. However, the taxonomic description and identification of these small (<15 μm) spherical or elliptical coccoid cells is difficult due to the lack of characteristic morphologic features. In addition to molecular investigations, biochemical criteria are employed to distinguish between the numerous “Chlorella” species, of which the sterol composition seems to be a reliable chemotaxonomic marker within several groups of these morphologically similar algae. In this study, the distribution of ergosterol was examined in 20 species of the “true” genus Chlorella and more distant “Chlorella” species using HPLC. Ergosterol in concentrations up to 4.5 μg · mg−1 dry weight (dwt) was detected in nine species, which are all related representatives of the Chlorellaceae. More distant relatives within the Trebouxiophyceae or representatives of the Chlorophyceae did not contain ergosterol. The results coincide with the latest molecular investigations of the genus Chlorella and further promote the potential of ergosterol as chemical marker to differentiate between members of the Chlorellaceae and other “Chlorella-like” species.