A taxonomic note on the genus Lactobacillus: Description of 23 novel genera, emended description of the genus Lactobacillus Beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae

TLDR

The Lactobacillus genus contains 261 diverse species, and the term “lactobacilli” will continue to refer to all organisms formerly classified in Lactobacillaceae until 2020. This study evaluated the taxonomy of Lactobacillaceae and Leuconostocaceae based on whole‑genome sequences. The authors used core genome phylogeny, conserved amino‑acid identity, clade‑specific signature genes, physiological traits, and ecological data to assess taxonomy. The polyphasic analysis led to reclassifying Lactobacillus into 25 genera—including an emended Lactobacillus and 23 new genera—and expanding the Lactobacillaceae family to encompass all former Lactobacillaceae and Leuconostocaceae members, thereby aligning taxonomy with phylogeny and grouping organisms into clades with shared ecological and metabolic traits.

Abstract

The genus Lactobacillus comprises 261 species (at March 2020) that are extremely diverse at phenotypic, ecological and genotypic levels. This study evaluated the taxonomy of Lactobacillaceae and Leuconostocaceae on the basis of whole genome sequences. Parameters that were evaluated included core genome phylogeny, (conserved) pairwise average amino acid identity, clade-specific signature genes, physiological criteria and the ecology of the organisms. Based on this polyphasic approach, we propose reclassification of the genus Lactobacillus into 25 genera including the emended genus Lactobacillus , which includes host-adapted organisms that have been referred to as the Lactobacillus delbrueckii group, Paralactobacillus and 23 novel genera for which the names Holzapfelia , Amylolactobacillus , Bombilactobacillus , Companilactobacillus , Lapidilactobacillus , Agrilactobacillus , Schleiferilactobacillus , Loigolactobacilus , Lacticaseibacillus , Latilactobacillus , Dellaglioa , Liquorilactobacillus , Ligilactobacillus , Lactiplantibacillus , Furfurilactobacillus , Paucilactobacillus , Limosilactobacillus , Fructilactobacillus , Acetilactobacillus , Apilactobacillus , Levilactobacillus , Secundilactobacillus and Lentilactobacillus are proposed. We also propose to emend the description of the family Lactobacillaceae to include all genera that were previously included in families Lactobacillaceae and Leuconostocaceae . The generic term ‘lactobacilli’ will remain useful to designate all organisms that were classified as Lactobacillaceae until 2020. This reclassification reflects the phylogenetic position of the micro-organisms, and groups lactobacilli into robust clades with shared ecological and metabolic properties, as exemplified for the emended genus Lactobacillus encompassing species adapted to vertebrates (such as Lactobacillus delbrueckii , Lactobacillus iners , Lactobacillus crispatus , Lactobacillus jensensii , Lactobacillus johnsonii and Lactobacillus acidophilus ) or invertebrates (such as Lactobacillus apis and Lactobacillus bombicola ).