Streptomyces asenjonii sp. nov., isolated from hyper-arid Atacama Desert soils and emended description of Streptomyces viridosporus Pridham et al. 1958

Abstract

A polyphasic study was undertaken to establish the taxonomic status of Streptomyces strains isolated from hyper-arid Atacama Desert soils. Analysis of the 16S rRNA gene sequences of the isolates showed that they formed a well-defined lineage that was loosely associated with the type strains of several Streptomyces species. Multi-locus sequence analysis based on five housekeeping gene alleles showed that the strains form a homogeneous taxon that is closely related to the type strains of Streptomyces ghanaensis and Streptomyces viridosporus. Representative isolates were shown to have chemotaxonomic and morphological properties consistent with their classification in the genus Streptomyces. The isolates have many phenotypic features in common, some of which distinguish them from S. ghanaensis NRRL B-12104^T, their near phylogenetic neighbour. On the basis of these genotypic and phenotypic data it is proposed that the isolates be recognised as a new species within the genus Streptomyces, named Streptomyces asenjonii sp. nov. The type strain of the species is KNN35.1b^T (NCIMB 15082^T = NRRL B-65050^T). Some of the isolates, including the type strain, showed antibacterial activity in standard plug assays. In addition, MLSA, average nucleotide identity and phenotypic data show that the type strains of S. ghanaensis and S. viridosporus belong to the same species. Consequently, it is proposed that the former be recognised as a heterotypic synonym of the latter and an emended description is given for S. viridosporus.

Keywords: Atacama Desert; Hyper-arid; Polyphasic taxonomy; Streptomyces.

Fig. 1

Maximum-likelihood phylogenetic tree based on 16S rRNA sequences showing relationships between isolates KNN6.11a, KNN 35.1b, KNN 35.2b, KNN 42.f, KNN 48.3, and KNN83.e and between them and the type strains of the most closely related Streptomyces species, the tree was inferred using the GTR+GAMMA model. The branches are scaled in terms of the expected number of substitutions per site. The numbers above the branches are support values when larger than 60% from ML (left) and MP (right) bootstrapping

Fig. 2

Subtree from the Streptomyces phylogenetic tree inferred from concatenated partial sequences of the house-keeping genes atpD, gyrB, recA, rpoB and trpB in IQ-Tree version 1.4.2 (Nguyen et al. 2015) as described by Labeda et al. (2017). Bootstrap values less than 95% were omitted as suggested by the IQ-Tree developers. Bar scale reflects number of substitutions per site

Fig. 3

Scanning electron micrograph of isolate KNN35-1b^T showing hairy ornamented spores in open spirals following growth on oatmeal agar at 28 °C for 14 days. Bar 1 µm