Two novel species of rapidly growing mycobacteria: Mycobacterium lehmannii sp. nov. and Mycobacterium neumannii sp. nov.

Abstract

Two rapidly growing mycobacteria with identical 16S rRNA gene sequences were the subject of a polyphasic taxonomic study. The strains formed a well-supported subclade in the mycobacterial 16S rRNA gene tree and were most closely associated with the type strain of Mycobacterium novocastrense. Single and multilocus sequence analyses based on hsp65, rpoB and 16S rRNA gene sequences showed that strains SN 1900^T and SN 1904^T are phylogenetically distinct but share several chemotaxonomic and phenotypic features that are are consistent with their classification in the genus Mycobacterium. The two strains were distinguished by their different fatty acid and mycolic acid profiles, and by a combination of phenotypic features. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values for strains SN 1900^T and SN 1904^T were 61.0 % and 94.7 %, respectively; in turn, the corresponding dDDH and ANI values with M. novocastrense DSM 44203^T were 41.4 % and 42.8 % and 89.3 % and 89.5 %, respectively. These results show that strains SN1900^T and SN 1904^T form new centres of taxonomic variation within the genus Mycobacterium. Consequently, strains SN 1900^T (40^T=CECT 8763^T=DSM 43219^T) and SN 1904^T (2409^T=CECT 8766^T=DSM 43532^T) are considered to represent novel species, for which the names Mycobacteriumlehmannii sp. nov. and Mycobacteriumneumannii sp. nov. are proposed. A strain designated as 'Mycobacteriumacapulsensis' was shown to be a bona fide member of the putative novel species, M. lehmannii.