Genomic and phenomic differentiation of Rhodococcus equi and related strains

16S rDNA sequence and pyrolysis mass spectrometric analyses were carried ou t on representatives of Rhodococcus equi and marker strains of genera that encompass mycolic acid containing actinomycetes. The R. equi strains formed a monophyletic clade within the evolutionary radiation occupied by members of the genera Nocardia and Rhodococcus. The 16S rDNA sequence data also sh owed R. equi to be an heterogeneous taxon. This heterogeneity was underscor ed by the pyrolysis mass spectrometric data. These observations are in line with those of previous studies where similar profiles of relatedness were found between pyrolysis mass spectral data and the results of DNA:DNA pairi ng and numerical phenetic studies.