Bock, Christina; krienitz, Lothar; Pröschold, Thomas:

Taxonomic reassessment of the genus Chlorella (Trebouxiophyceae) using molecular signatures (barcodes), including description of seven new species

In: Fottea : journal of the Czech Phycological Society., Jg. 11 (2011) ; Nr. 2, S. 293–312
ISSN: 1802-5439
Zeitschriftenaufsatz / Fach: Biologie
Fakultät für Biologie » Allgemeine Botanik
After the description of Chlorella vulgaris by Beijerinck, 120 years ago, members of the genus Chlorella
belong to the best studied green algae worldwide. However, numerous open questions remained regarding
their systematics. Recent molecular studies showed the polyphyly of the genus within the Chlorophyceae and
Trebouxiophyceae. Chlorella–species were traditionally characterized by spherical to oval cell shape, solitary life–
form and the absence of mucilaginous envelopes. The challenge in the past was how to distinguish species due to
their high phylogenetic diversity combined with a limited amount of morphological characters. Using a polyphasic
approach of SSU– and ITS rDNA phylogeny, secondary structure of the ITS and light microscopic observations,
we were able to detect six lineages with Dictyosphaerium–like strains in close relationship to C. vulgaris, here
described or combined newly as C. coloniales sp. nov., C. pituita sp. nov., C. pulchelloides sp. nov., C. singularis
sp. nov., C. elongata comb. nov. and C. chlorelloides comb. nov. Furthermore, three new species without mucilage
were described as C. lewinii sp. nov., C. rotunda sp. nov. and C. volutis sp. nov. Using the 5.8S rRNA and part of
the ITS–2 as molecular signature (barcode), we were able to distinguish not only the five already known species of
Chlorella, C. vulgaris, C. sorokiniana, C. heliozoae, C. lobophora and C. variabilis but the seven new species and
two new combinations as well. CBCs and hemi–CBCs within the secondary structure of the ITS–2 confirmed the
separation of the species. Our study led to a new understanding of the evolution of morphology within the genus Chlorella and to an emendation of the generic description