Yersinia kristensenii consists of phenotypically heterogeneous strains. This is reflected by the existence of strains with various multilocus enzyme electrophoresis and 16S rRNA gene sequence types. Strains originally phenotyped as members of Y. kristensenii were studied using 16S rRNA gene sequencing, DNA-DNA hybridization, determination of the DNA base composition and various phenotypic tests. The results were compared to those of Yersinia type strains. Based on levels of DNA-DNA relatedness, a specific 16S rRNA gene sequence type and the presence of lysine decarboxylase activity, a novel species, Yersinia aleksiciae sp. nov., is proposed. The type strain is Y159(T) (=WA758(T)=DSM 14987(T)=LMG 22254(T)).