Biochemical Contributions to the Taxonomy of the Genus Chlorella

Abstract

SINCE Warburg's1 work, in 1919, green algae of the genus Chlorella have been among the experimental organisms most frequently used for plant physiological and biochemical research. However, due to the little morphological differentiation of their more or less spherical cells, the taxonomy of these algae has been rather confused (cf. ref. 2). This holds especially true for the members of the section Euchlorella comprising the most common species, that is, Chlorella vulgaris Beijerinck, Chl. pyrenoidosa Chick, and Chl. ellipsoidea Gerneck. The criteria given by Pascher3 for their identification (size and shape of cells and chloroplasts, visibility of the pyrenoid, etc.) have been shown to be highly variable and ambiguous, and to depend to a large extent on culture conditions and developmental stage of the cells4. Therefore, in most cases it is very difficult, if not impossible, to identify these species by morphological criteria. Since the characteristics traditionally used for taxonomy are obviously insufficient in this case, we propose to use mainly physiological and biochemical rather than morphological criteria for the identification of these Chlorella species.