Respiration of tritiated substrates in heterotrophic activity assays.

The respiration percentage of H-labeled glucose by heterotrophic microorganisms in water samples was determined by a method based on equimolar addition of [H]- and [C]glucose to samples. The respiration percentage of [H]glucose exceeded that of [C]glucose by 10% over the assayed range of respiration rates. Respiration percentages diminished with decreasing temperature, the relation between respiration of [H]- and [C]glucose remaining the same. The significance of tritiated water respiration with regard to experimental design is emphasized.