SULFIDE TOLERANCE IN HETEROMASTUS-FILIFORMIS (POLYCHAETA) - MITOCHONDRIAL ADAPTATIONS

Isolated mitochondria of Heteromastus filiformis detoxified sulphide. The mechanism worked best at low concentrations of up to 10 mumol l-1 sulphide. Sulphide inhibited mitochondrial cytochrome c oxidase in vit ro at nanomolar concentrations (K(i): 0.37 +/- 0.17 mumol l-1), while catalase, another metal-containing enzyme, had a much higher inhibitio n constant (K(i): 790 +/- 164 mumol l-1). Isolated mitochondria phosph orylated ADP using sulphide as substrate. The process had a maximum at 10 mumol l-1 sulphide (about 8 nmol ATP mg protein-1 min-1) H. filifo rimis has a high anaerobic capacity and may accumulate up to 10.55 +/- 1.06 mumol succinate g fresh mass-1 after 24 hours of hypoxia. We con clude that the worms switch to anaerobiosis to survive oxygen deficien cy or periods in which the ambient sulphide levels are too high to per mit detoxification by the mitochondria. These results are discussed in terms of hydrogen sulphide acting either as a toxic substance or as b eing useful in the species' energy metabolism.