The nomenclatural types of the orders Acholeplasmatales, Halanaerobiales, Halobacteriales, Methanobacteriales, Methanococcales, Methanomicrobiales, Planctomycetales, Prochlorales, Sulfolobales, Thermococcales, Thermoproteales and Verrucomicrobiales are the genera Acholeplasma, Halanaerobium, Halobacterium, Methanobacterium, Methanococcus, Methanomicrobium, Planctomyces, Prochloron, Sulfolobus, Thermococcus, Thermoproteus and Verrucomicrobium, respectively. Opinion 79

The Judicial Commission of the International Committee on Systematics of Prokaryotes has corrected the nomenclatural types for 12 prokaryotic orders that previously violated the Bacteriological Code. The correction addressed a systematic error where families, rather than genera, had been designated as nomenclatural types for these orders. Following a formal Request for an Opinion by Euzbéby and Tindall, the Commission established genera as the proper nomenclatural types for each order: Acholeplasma for Acholeplasmatales, Halanaerobium for Halanaerobiales, Halobacterium for Halobacteriales, Methanobacterium for Methanobacteriales, Methanococcus for Methanococcales, Methanomicrobium for Methanomicrobiales, Planctomyces for Planctomycetales, Prochloron for Prochlorales, Sulfolobus for Sulfolobales, Thermococcus for Thermococcales, Thermoproteus for Thermoproteales, and Verrucomicrobium for Verrucomicrobiales. This nomenclatural correction ensures compliance with Rules 15 and 21a of the Bacteriological Code and standardizes microbial taxonomy across these diverse prokaryotic groups.

Key findings

• The Judicial Commission corrected nomenclatural types for 12 prokaryotic orders that previously violated the Bacteriological Code by using families instead of genera as types
• Each of the 12 orders now has a proper genus designated as its nomenclatural type, from both bacterial and archaeal lineages
• The correction includes methanogens, halophiles, thermophiles, and other physiologically diverse prokaryotes, establishing consistent taxonomic standards across different prokaryotic groups
• This nomenclatural decision ensures compliance with Rules 15 and 21a of the 1990 Revision of the Bacteriological Code