RESPIRATORY METABOLISM IN A MARINE DINOFLAGELLATE

¹ Dept. of Zoology, Duke University, Durham, N.C.
² Woods Hole Oceanographic Institution, Woods Hole, Mass.

1. The effects of various inhibitors and substrates on the respiration of suspensions of Gymnodinium were tested. Iodoacetate, arsenite, malonate, fluoroacetate azide and cyanide all inhibited the endogenous rate to some extent. Malonate and fluoroacetate were most potent. Cells grown in cycles of alternating light and dark were most sensitive to malonate during the middle of the light-period and at the beginning of the dark-period. Most of the glycolytic intermediates used did not affect the endogenous respiratory rate. Krebs cycle intermediates either increased the respiratory rate (succinate, malate, fumarate) or markedly decreased it (oxaloacetate, citrate, -ketoglutarate). With the exception of an increased O₂ consumption in the presence of glutamate, alanine, and cysteine, the O₂ uptake of Gymnodinium was unaffected by the amino acids tested.

2. Ascorbate and reduced glutathione increased O₂ uptake profoundly. This uptake was further stimulated by cyanide and arsenite; it was insensitive to diethyldithiocarbamate and azide; it was completely blocked by cysteine, EDTA malonate and fluoroacetate.