An ANI gap within bacterial species that advances the definitions of intra-species units

作者：Luis M. Rodriguez‐R, Roth E. Conrad, Tomeu Viver, Dorian J. Feistel, Blake G. Lindner, Stephanus N. Venter, Luis H. Orellana, Rudolf Amann, Ramon Rosselló‐Móra, Konstantinos T. Konstantinidis · 发表于：mBio · 年份：2023 · DOI：10.1128/mbio.02696-23 · 被引用次数：212 · 研究领域：Genomics and Phylogenetic Studies、Antibiotic Resistance in Bacteria、Probiotics and Fermented Foods

ABSTRACT Large-scale surveys of prokaryotic communities (metagenomes), as well as isolate genomes, have revealed that their diversity is predominantly organized in sequence-discrete units that may be equated to species. Specifically, genomes of the same species commonly show genome-aggregate average nucleotide identity (ANI) >95% among themselves and ANI <90% to members of other species, while genomes showing ANI 90%–95% are comparatively rare. However, it remains unclear if such “discontinuities” or gaps in ANI values can be observed within species and thus used to advance and standardize intra-species units. By analyzing 18,123 complete isolate genomes from 330 bacterial species with at least 10 genome representatives each and available long-read metagenomes, we show that another discontinuity exists between 99.2% and 99.8% (midpoint 99.5%) ANI in most of these species. The 99.5% ANI threshold is largely consistent with how sequence types have been defined in previous epidemiological studies but provides clusters with ~20% higher accuracy in terms of evolutionary and gene-content relatedness of the grouped genomes, while strains should be consequently defined at higher ANI values (>99.99% proposed). Collectively, our results should facilitate future micro-diversity studies across clinical or environmental settings because they provide a more natural definition of intra-species units of diversity. IMPORTANCE Bacterial strains and clonal complexes are two cornerstone concepts...