PHYLOGENETIC ANALYSIS AND TAXONOMIC HISTORY OF NOCARDIA-PINENSIS AND NOCARDIA-AMARAE

Nocardia pinensis and N. amarae are nocardioform actinomycetes that pr edominate in and stabilize biological foams on the surface of aeration tanks in activated sludge sewage treatment processes. Their taxonomy is confused since it is difficult to align them with known nocardiofor m actinomycete genera based upon chemotaxonomic, numerical taxonomic o r phenetic information. A review of this information is provided to de monstrate the difficulties. We have sequenced the 16S rRNA gene (16S r DNA) of the type strains of N. pinesis and N. amarae and compared thes e with representative nocardioform actinomycete sequences. N. amarae w as most closely related to and had the highest sequence similarity wit h Gordona terrae. The support in our phylogenetic analysis for this wa s significant (bootstrap values of 99-100%). This is consistent with r ecent publications placing N. amarae into the genus Gordona. N. pinens is was most closely related to G. terrae and N. amarae and was an outl ier to the Gordona group. However, further analyses which included Gor dona bronchialis indicated thar N. pinensis may nor be firmly related to the genus Gordona.