Biochemical and Evolutionary Aspects of Eukaryotes That Inhabit Sulfidic Environments

Abstract

Various eukaryotes inhabit environments that harbor high concentrations of sulfide, which is a potent inhibitor of complex IV in the mitochondrial respiratory chain. They must therefore posses means by which they can detoxify sulfide, or use alternative electron routes that circumvent oxygen as the terminal acceptor, or both. The biochemical mechanisms through which eukaryotes deal with sulfide are be-inning to come into focus, with sulfide:quinone oxidoreductase and the energy metabolism germane to anaerobic mitochondria standing in the foreground. This chapter briefly covers current progress in understanding the biochemistry of sulfide detoxification and utilization by eukaryotes. In light of newer views of ocean geo-chemistry ("Canfield" oceans), both the anaerobic biochemistry of mitochondria and their capacity to deal with sulfide are most easily interpreted as evolutionary holdovers from the anoxic and sulfidic phase of ocean history between about 2.3 billion and about 0.6 billion years ago.