This document records the minutes from the September 2001 meetings of the International Committee on Systematics of Prokaryotes Subcommittee on Halobacteriaceae taxonomy, held in Seville, Spain. The subcommittee reviewed and approved multiple new halophilic archaeal taxa, including new species within genera such as Natrialba, Natrinema, and Haloterrigena, along with new genera Halorhabdus and Halosimplex. The group addressed nomenclatural issues, including a correction to the naming of Natrialba aegyptiaca and identification of species incertae sedis requiring formal description. A significant taxonomic rearrangement involved transferring Haloarcula mukohataei to a new genus, Halomicrobium, based on distinct polar lipid composition and phylogenetic distance. The subcommittee also discussed overlapping characteristics between Haloterrigena and Natrinema genera, recommending further phenotypic characterization. Additional agenda items included efforts to remove mislabeled strains from culture collection catalogs, preservation of historically important halophile strains from a discontinued Canadian collection, and discussion of prokaryotic species concepts relevant to Halobacteriaceae taxonomy.

Key findings

• Multiple new halophilic archaeal taxa were approved, including several new Natrialba species and the new genera Halorhabdus and Halosimplex
• Haloarcula mukohataei was reclassified into a new genus, Halomicrobium, based on distinct polar lipid composition and phylogenetic analysis
• The subcommittee identified need for taxonomic rearrangement within Haloterrigena and Natrinema genera due to overlapping characteristics and recommended further phenotypic study
• Efforts were made to correct mislabeled and invalid strain names in major culture collections (ATCC and NCIMB)
• Historically important halophile strains from a discontinued Canadian culture collection were recovered and preserved, with 20 of 28 cultures proving viable