[Investigations concerning the role of folic acid in the metabolism of autotrophic cells].

The role of folic acid in metabolism was studied in mass cultures of Chlorella pyrenoidosa, especially with respect to its possible participation in early stages of photosynthetic CO2-fixation. Sulfonamides (sulfanilamide, sulfathiazole) were used as specific antimetabolites in the biosynthesis of folic acid.After 24 hours the number of cell divisions was much more diminished than the pigment and nucleic acid content of the cells. Significant inhibition of mass production did not occur before 48 hours. This difference in the sensitivity of cell division and mass production towards the antimetabolite leads to a definite increase in cell size.Antimetabolites administered together with (10(-6) mol/l) p-aminobenzoic acid or (10(-5) mol/l) folic acid cause no inhibition.The harmful effect of the sulfonamide is strictly reversible; the speed of recovery depends on the p-aminobenzoic acid concentration. (14)C-Fixation experiments gave no evidence for the participation of folic acid enzymes in primary processes of photosynthetic carbon uptake. The decline of the fixation rate may be interpreted as a secondary effect on the enzyme apparatus necessary for photosynthesis.The enormous increase of the sugar content in the individual cells indicates a general disturbance of the metabolism.