Streptomyces thermocarboxydovorans sp. nov. and Streptomyces thermocarboxydus sp. nov., two moderately thermophilic carboxydotrophic species from soil.

Four moderately thermophilic, carboxydotrophic streptomycetes were the subject of a comparative taxonomic investigation designed to establish their taxonomic relationships. Almost complete sequences of the 16S rRNA genes of the test strains were determined following the isolation and direct sequencing of the amplified genes. The resultant nucleotide sequences were aligned with the sequences of previously studied streptomycetes, and phylogenetic trees generated by using the neighbour-joining, Fitch-Margoliash, maximum-likelihood and maximum-parsimony methods. It was evident from the phylogenetic analyses that strains AT50, AT51 and AT52 were most closely related to Streptomyces thermodiastaticus DSM 40573T and strain AT37 to Streptomyces glaucescens DSM 40716 and Streptomyces pseudogriseolus NRRL 3985. Random DNA amplification profiles clearly distinguished strains AT50, AT51 and AT52 from Streptomyces thermodiastaticus and from strain AT37. The molecular systematic evidence, together with phenotypic data derived from this and previous studies, indicate that the test strains merit species status within the genus Streptomyces. The name Streptomyces thermocarboxydovorans sp. nov. is proposed for strains AT50, AT51 and AT52 (type strain) and Streptomyces thermocarboxydus sp. nov. for strain AT37.