Whole genome analysis calls for a taxonomic rearrangement of the genus Colwellia.

Microbial taxonomy is the foundation of microbiology and rapid advancements in DNA sequencing technologies are providing new approaches to address prevailing questions in this field. The family Colwelliaceae, which currently comprises four genera, is a diverse and globally abundant group of Gamaproteobacteria. Based on 14 publically available genomes of bacteria strains labeled as members of the family Colwelliaceae, phylogenomic analyses were conducted to revisiting the taxonomic status of this family both in the genus and species level. Using genome-based phylogeny as a primary guideline and genome-based similarity indexes including average amino acid identity, percentage of conserved proteins, average nucleotide identity, and the digital DNA-DNA hybridization as supplements, the following taxonomic proposals were proposed: Colwellia polaris, Colwellia beringensis, Colwellia sediminilitoris, Colwellia aestuarii, Colwellia chukchiensis and Colwellia mytili should be reclassified into the novel genus Cognaticolwellia; Colwellia agarivorans should be reclassified into the novel genus Pseudocolwellia. Our results constitute a solid framework for current and future taxonomic decisions within this family, which will be helpful for avoiding confusion with ecological and evolutionary interpretations in subsequent studies.