Sulphide tolerance in Heteromastus filiformis (Polychaeta): Mitochondrial adaptations

Abstract

Isolated mitochondria of Heteromastus filiformis detoxified sulphide. The mechanism worked best at low concentrations of up to 10 µmol l^-1 sulphide. Sulphide inhibited mitochondrial cytochrome c oxidase in vitro at nanomolar concentrations (K_i: 0.37 ± 0.17 µmol l^-1) , while catalase, another metal- containing enzyme, had a much higher inhibition constant (K_i: 790 ± 1ú4 µmol l^-l). Isolated mitochondria phosphorylated ADP using sulphide as substrate. The process had a maximum at 10 µmol l^-1 sulphide (about 8 nmol ATP mg protein^-1 min^-1) H. filiforimis has a high anaerobic capacity and may accumulate up to 10.55 ± 1.06 µmol succinate g fresh mass^-1 after 24 hours of hypoxia. We conclude that the worms switch to anaerobiosis to survive oxygen deficiency or periods in which the ambient sulphide levels are too high to permit detoxification by the mitochondria. These results are discussed in terms of hydrogen sulphide acting either as a toxic substance or as being useful in the species' energy metabolism.