Prokaryotic strains contributing proposals of new phyla and kingdoms

2026/02/16

Currently, the International Code of Nomenclature of Prokaryotes (ICNP) covers the high-level taxonomic ranks “phylum”, “kingdom” and “domain.” There are two domains – Bacteria and Archaea – with four kingdoms formally approved within each domain. One of the four archaeal kingdoms is Nanobdellati. Our research group previously reported Nanobdella aerobiophila ^T (=JCM 33616^T), which is the origin of this kingdom name. In 2024, another archaeal kingdom Promethearchaeati was validated based on Promethearchaeum syntrophicum MK-D1^T (=JCM 39240^T). Meanwhile, in the domain Bacteria, proposals for new phyla have been recently made one after another, such as the phylum Minisyncoccota, formerly referred to as the CPR (Candidate Phyla Radiation) clade, and the phylum Fidelibacterota, previously known as the ‘Marine Group A’ or SAR406 group. Both phylum names are derived from the genus names of Minisyncoccus archaeiphilus PMX.108^T (=JCM 39522^T) and Fidelibacter multiformis IA91^T (=JCM 39387^T), respectively. All the above species show special characteristics that could only be demonstrated through cultivation, such as obligate symbiosis with attachment to the cell surface of a specific host, formation of protrusions, or inability to grow without utilizing specific cellular components of other organisms. These reports have provided important insights not only for taxonomy but for whole microbiology, including physiology, ecology, and evolution. At present, strains MK-D1^T and PMX.108^T are only available from JCM among numerous international culture collections. JCM provides phylogenetically and physiologically diverse strains, in addition to the above strains, as live cultures to the scientific community.

References:
Kato et al. 2022. Nanobdella aerobiophila gen. nov., sp. nov., a thermoacidophilic, obligate ectosymbiotic archaeon, and proposal of Nanobdellaceae fam. nov., Nanobdellales ord. nov. and Nanobdellia class. nov.
Int. J. Syst. Evol. Microbiol. 72: 005489.
DOI: 10.1099/ijsem.0.005489

Imachi et al. 2024. Promethearchaeum syntrophicum gen. nov., sp. nov., an anaerobic, obligately syntrophic archaeon, the first isolate of the lineage ‘Asgard’ archaea, and proposal of the new archaeal phylum Promethearchaeota phyl. nov. and kingdom Promethearchaeati regn. nov.
Int. J. Syst. Evol. Microbiol. 74: 006435.
DOI: 10.1099/ijsem.0.006435

Katayama et al. 2024. Fidelibacter multiformis gen. nov., sp. nov., isolated from a deep subsurface aquifer and proposal of Fidelibacterota phyl. nov., formerly called Marine Group A, SAR406 or Candidatus Marinimicrobia.
Int. J. Syst. Evol. Microbiol. 74: 006558.
DOI: 10.1099/ijsem.0.006558

Nakajima et al. 2025. Minisyncoccus archaeiphilus gen. nov., sp. nov., a mesophilic, obligate parasitic bacterium and proposal of Minisyncoccaceae fam. nov., Minisyncoccales ord. nov., Minisyncoccia class. nov. and Minisyncoccota phyl. nov. formerly referred to as Candidatus Patescibacteria or candidate phyla radiation.
Int. J. Syst. Evol. Microbiol. 75: 006668.
DOI: 10.1099/ijsem.0.006668

Phylogenetic tree of whole prokaryotes (left) and representative strains of novel phyla and kingdoms (right).

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