Reclassification of Actinobacillus muris as Muribacter muris gen. nov., comb. nov.

To reinvestigate the taxonomy of [Actinobacillus] muris, 474 strains, mainly from mice and rats, were characterized by phenotype and 130 strains selected for genotypic characterization by 16S rRNA and partial rpoB gene sequencing. The type strain was further investigated by whole-genome sequencing. Phylogenetic analysis of the DNA sequences showed one monophyletic group with intragroup similarities of 96.7 and 97.2 % for the 16S rRNA and rpoB genes, respectively. The highest 16S rRNA gene sequence similarity to a taxon with a validly published name outside the group was 95.9 %, to the type strain of [Pasteurella] pneumotropica. The closest related taxon based on rpoB sequence comparison was 'Haemophilus influenzae-murium', with 88.4 % similarity. A new genus and a new combination, Muribacter muris gen. nov., comb. nov., are proposed based on a distinct phylogenetic position based on 16S rRNA and rpoB gene sequence comparisons, with major divergence from the existing genera of the family Pasteurellaceae. The new genus has the characteristics of [A.] muris with the emendation that acid formation from ( - )-d-mannitol and hydrolysis of aesculin are variable, while the α-glucosidase test is positive. There is no requirement for exogenously supplied NAD (V factor) for the majority of strains investigated; however, one strain was found to require NAD. The major fatty acids of the type strain of Muribacter muris were C14 : 0, C14 : 0 3-OH/iso-C16 : 1 I, C16 : 1ω7c and C16 : 0, which is in line with most genera of the Pasteurellaceae. The type strain of Muribacter muris is CCUG 16938T ( = NCTC 12432T = ATCC 49577T).