Abstract
The Judicial Commission of the International Committee on Systematics of Prokaryotes has decided to place the genus Methanothrix with the species Methanothrix soehngenii Huser et al. 1983 on the list of nomina rejicienda, based on the fact that it is not represented by an axenic culture and contravenes Rule 31a of the International Code of Nomenclature of Bacteria. The species Methanothrix thermophila is transferred to the genus Methanosaeta as Methanosaeta thermophila (Kamagata et al. 1992) Boone and Kamagata 1998 comb. nov.
In publishing this Opinion, the Judicial Commission of the International Committee on Systematics of Prokaryotes has considered the Request for an Opinion by Boone & Kamagata (1998) in order to clarify the nomenclatural confusion associated with the genera Methanothrix and Methanosaeta.
In 1980, Zehnder et al. (1980) characterized an acetate-decarboxylating, non-hydrogen-oxidizing methane bacterium with the morphological and metabolic properties of a filament-forming rod, which often occurred in bundles, that had been first recognized by the Dutch microbiologist N. L. Söhngen in 1910. Since then, organisms with this morphology enriched from sludge digestors have been reported many times in studies on methane formation and referred to as the fat rod or Methanobacterium soehngenii. In 1982, Huser et al. (1982) published a formal description and named the organism Methanothrix soehngenii as the single species of the new genus Methanothrix. Strain Opfikon (=DSM 2139) was designated the type strain. However, this organism is not a pure culture and contravenes Rule 31a of the International Code of Nomenclature of Bacteria (the Code) (Lapage et al., 1992). Rule 31a states: