These results indicate a potentially significant level of horizontal gene transfer among Acinetobacter species and illustrate an inability to delineate species based on gene content comparison only. These findings suggest that ANI analyses provide results that are compatible with traditional and phylogenetic classifications, whereas K-string and genome fluidity approaches

appear to be too strongly influenced by the effects of horizontal gene transfer to be consistent with previously accepted approaches. Defining species in Acinetobacter on the basis of whole-genome analyses The congruence of the phylogenetic tree and ANI dendogram with each other and with existing Ku-0059436 species definitions provides confidence

that these techniques are fit for purpose in delineating species in the absence of phenotypic data. Furthermore, as Goris et al. suggest, the ANI approach provides a handy numerical cut-off at 95% identity to demarcate species boundaries, which corresponds to the 70% DDH value [10]. When we applied selleck compound this cut-off to our dataset, we were able to classify 37 of the strains into thirteen previously named species. In line with the likely misclassification of strains, we observed that A. nosocomialis NCTC 10304 shares phylogenetic history and exhibits pair-wise ANI values greater than 95% with all 14 sequenced A. baumannii strains, thus confirming it should be designated A. baumannii NCTC 10304. Similar arguments apply for A. calcoaceticus PHEA-2 (new designation A. pittii PHEA-2) and A. sp. ATCC 27244 (A. haemolyticus ATCC 27244). However, the strain NCTC 7422 appears to be distinctive enough to represent new species. While the traditional polyphasic approach to taxonomy demands additional phenotypic characterization before these species can be named, on the basis of the analyses presented here, we isometheptene propose the species name Acinetobacter bruijnii sp. nov. (N. L. gen. masc. n. bruijnii, of Bruijnius, named

after Nicolaas Govert de Bruijn, Dutch mathematician) for strain NCTC 7422 and all future strains that are monophyletic and show ≥ 95% ANI to this strain. It is interesting to note that our results based on core genome and ANI analyses differ from those based on AFLP patterns [56]; notably in the latter A. haemolyticus and A. junii do not cluster together nor does the cluster form a sister branch to the ACB complex; also A. johnsonii does not appear on the same deep-branch as A. lwoffii. This observation suggests that although AFLP is adept at species resolution, it appears to be unsuitable for phylogenetic analysis. Several recent studies report alternative genomic approaches to bacterial taxonomy and species identification.