Physiological and biochemical contributions to the taxonomy of the genus Chlorella

1. Rabbit antisera to soluble cytochrome c-553 and to ferredoxin were characterized by double immunodiffusion, the antiserum to cytochrome c-553 also by immuno-electrophoresis and by the quantitative precipitation reaction.
2. Soluble cytochromes c-553 were isolated from 11 strains of Chlorella belonging to 8 species and from one strain of Scenedesmus. Their reactivity with antiserum to soluble cytochrome c-553 from Chlorella fusca var. vacuolata 211-8b was studied.
3. With the double immunodiffusion method, the soluble cytochromes c-553 from C. fusca var. vacuolata 211-8b, C. fusca var. rubescens 232/1, C. fusca var. fusca 343, and Scenedesmus obliquus 276-3b appear immunologically identical.
4. The soluble cytochromes c-553 from C. zofingiensis 211-14a, 211-14b, and 211-14c show in the cross reaction a partial immunological relationship with that from C. fusca var. vacuolata 211-8b.
5. The soluble cytochromes c-553 from C. sorokiniana 211-8k, C. vulgaris 211-11c and 211-19, C. saccharophila 211-1 a, and C. homosphaera 211-8e (Ca.) do not show a cross reaction with that from C. fusca var. vacuolata 211-8b.
6. These results indicate that not only C. fusca var. fusca, but also C. fusca var. vacuolata, C. fusca var. rubescens, and possibly C. zofingiensis might be more closely related to the genus Scenedesmus than to the Chlorella species of the “C. vulgaris group” (i.e., C. sorokiniana, C. vulgaris, and C. saccharophila).
7. An application of the double immunodiffusion method with an antiserum to ferredoxin from C. vulgaris 211-8m revealed that the ferredoxins from 20 strains of 9 Chlorella species and from one strain of Scenedesmus do not exhibit any immunological differences as compared to the homologous antigen.