Yersinia enterocolitica is the most diverse species among the Yersinia genera and shows more polymorphism, especially for the non-pathogenic strains. Individual non-pathogenic Y. enterocolitica strains are wrongly identified because of atypical phenotypes. In this study, we isolated an unusual Y. enterocolitica strain LC20 from Rattus norvegicus. The strain did not utilize urea and could not be classified as the biotype. API 20E identified Escherichia coli; however, it grew well at 25 °C, but E. coli grew well at 37 °C. We analyzed the genome of LC20 and found the whole chromosome of LC20 was collinear with Y. enterocolitica 8081, and the urease gene did not exist on the genome which is consistent with the result of API 20E. Also, the 16 S and 23 SrRNA gene of LC20 lay on a branch of Y. enterocolitica. Furthermore, the core-based and pan-based phylogenetic trees showed that LC20 was classified into the Y. enterocolitica cluster. Two plasmids (80 and 50 k) from LC20 shared low genetic homology with pYV from the Yersinia genus, one was an ancestral Yersinia plasmid and the other was novel encoding a number of transposases. Some pathogenic and non-pathogenic Y. enterocolitica-specific genes coexisted in LC20. Thus, although it could not be classified into any Y. enterocolitica biotype due to its special biochemical metabolism, we concluded the LC20 was a Y. enterocolitica strain because its genome was similar to other Y. enterocolitica and it might be a strain with many mutations and combinations emerging in the processes of its evolution.
Keywords: Comparative genome analysis; Complete genome sequence; Phylogenetic analysis; Yersinia.