The dynamic history of prokaryotic phyla: Discovery, diversity and division

Pallen, Mark J. ORCID: https://orcid.org/0000-0003-1807-3657 (2024) The dynamic history of prokaryotic phyla: Discovery, diversity and division. International Journal of Systematic and Evolutionary Microbiology, 74 (9). ISSN 1466-5026

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Abstract

Here, I review the dynamic history of prokaryotic phyla. Following leads set by Darwin, Haeckel and Woese, the concept of phylum has evolved from a group sharing common phenotypes to a set of organisms sharing a common ancestry, with modern taxonomy based on phylogenetic classifications drawn from macromolecular sequences. Phyla came as surprising latecomers to the formalities of prokaryotic nomenclature in 2021. Since then names have been validly published for 46 prokaryotic phyla, replacing some established names with neologisms, prompting criticism and debate within the scientific community. Molecular barcoding enabled phylogenetic analysis of microbial ecosystems without cultivation, leading to the identification of candidate divisions (or phyla) from diverse environments. The introduction of metagenome-assembled genomes marked a significant advance in identifying and classifying uncultured microbial phyla. The lumper–splitter dichotomy has led to disagreements, with experts cautioning against the pressure to create a profusion of new phyla and prominent databases adopting a conservative stance. The Candidatus designation has been widely used to provide provisional status to uncultured prokaryotic taxa, with phyla named under this convention now clearly surpassing those with validly published names. The Genome Taxonomy Database (GTDB) has offered a stable, standardized prokaryotic taxonomy with normalized taxonomic ranks, which has led to both lumping and splitting of pre-existing phyla. The GTDB framework introduced unwieldy alphanumeric placeholder labels, prompting recent publication of over 100 user-friendly Latinate names for unnamed prokaryotic phyla. Most candidate phyla remain ‘known unknowns’, with limited knowledge of their genomic diversity, ecological roles, or environments. Whether phyla still reflect significant evolutionary and ecological partitions across prokaryotic life remains an area of active debate. However, phyla remain of practical importance for microbiome analyses, particularly in clinical research. Despite potential diminishing returns in discovery of biodiversity, prokaryotic phyla offer extensive research opportunities for microbiologists for the foreseeable future.

Item Type: Article
Additional Information: Funding Information: M.J.P. is supported by UKRI grant CLIMB-BIG-DATA: A Cloud Infrastructure for Big-Data Microbial Bioinformatics, Project Reference: MR/T030062/1. No one employed by the funders, other than the author, played any role in the study or in the preparation of the article or decision to publish.
Uncontrolled Keywords: candidatus names,phylogenetics,prokaryotic nomenclature,prokaryotic phyla,prokaryotic taxonomy,shotgun metagenomics,ecology, evolution, behavior and systematics,microbiology ,/dk/atira/pure/subjectarea/asjc/1100/1105
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
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Depositing User: LivePure Connector
Date Deposited: 19 Sep 2024 11:30
Last Modified: 21 Nov 2024 03:31
URI: https://ueaeprints.uea.ac.uk/id/eprint/96776
DOI: 10.1099/ijsem.0.006508

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