Phylogeny of mycolic acid-containing actinomycetes

Almost-complete 16S rRNA sequences of 32 representatives of the genera Mycobacterium, Gordona, Mycobacterium, Nocardia, Rhodococcus, Tsukamurella and Turicella were examined using the neighbor-joining, Fitch-Margoli-ash, maximum parsimony and maximum likelihood methods in order to clarify the suprageneric relationships of these taxa, The topology of the resultant phylogenetic trees was only marginally affected by the use of the different algorithms. Several outgroup strains were used to try and establish the position of the root in the mycolata evolutionary tree, Most of the outgroup strains gave estimates of root positions that proved to be inconsistent when the different tree-making algorithms were used, However it was possible to assign the test strains to two suprageneric lineages the members of which can be distinguished using chemical markers, The family Corynebacteriaceae encompasses the genera Corynebacterium, Dietzia and Turicella and the family Mycobacteriaceae, the genera Gordona, Mycobacterium, Nocardia, Rhodococcus and Tsukamurella, Nocardia pinensis formed a distinct clade that was most closely related to the Gordona lineage, Emended descriptions are given of the two suprageneric taxa.