Carbon utilization patterns in the heterotrophic blue-green alga Chlorogloea fritschii

Summary

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• 1. The metabolic patterns of Chlorogloea fritschii, a blue-green alga capable of growing both heterotrophically and autotrophically, were analyzed in cells grown with different carbon and energy sources.

• 2. The distribution of isotopic carbon incorporated into cells grown on combinations of CO₂, sucrose and acetate in the light or in the dark was determined after cell fractionation and amino acid isolation. Fractionation studies indicated that C. fritschii utilizes organic substrates both in the light and the dark, but that the pattern of incorporation in the light is more similar to that seen in other bluegreen algae grown in the light than to its own pattern in the dark.

• 3. CO₂ is also incorporated into both light-and dark-grown cells, but sucrose is the preferred substrate when CO₂ and sucrose are both present.

• 4. Label from radioactive sucrose and acetate was distributed into all amino acids separated. Large amounts of label appeared in both the glutamate and aspartate families, suggesting that the Krebs cycle, which appears to be incomplete in other blue-greens, may be fully functional in C. fritschii in the light and in the dark.