Polyphasic identification and genome mining of secondary metabolites of a novel species Streptomyces haixigobicum sp. nov. Qhu-G9 isolated from the Gobi habitat of the Qinghai-Tibetan Plateau

Abstract:

[Background] The extreme habitats of the Qinghai-Tibet Plateau (QTP) harbor rich microbial resources and are important sources of microbial drugs, with abundant microbial resources remaining to be exploited.[Objective] A Streptomyces strain Qhu-G9 isolated from Gobi soil of the QTP was identified by polyphasic taxonomy, and its biosynthesis potential of secondary metabolites was analyzed. [Methods] The taxonomic status of Streptomyces Qhu-G9 was determined by 16S rRNA gene amplification, sequencing, and phylogenetic analysis, combined with polyphasic taxonomy based on genome sequencing and morphological, physiochemical, and cytochemical characteristics. [Results] Qhu-G9 had the highest similarity (99.22%) with the type strains Streptomyces dioscori A217^T and S. auranttⅡacus NBRC 13017^T, which, combined with morphological characteristics, indicated that Qhu-G9 belonged to Streptomyces. However, the phylogenetic tree constructed based on the 16S rRNA gene sequence displayed that Qhu-G9 branched independently. Moreover, the physiochemical and cytochemical characteristics of this strain were quite different from those of the most similar model bacteria. We then employed genome sequencing to evaluate the digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) between Qhu-G9 and the model bacteria. The dDDH and ANI values were the highest between Qhu-G9 and S. auranttⅡacus NBRC 13017^T, reaching 36.65% and 88.21%, respectively, both of which were lower than those determining a novel species. The results further confirmed that Qhu-G9 was a novel species of Streptomyces and named as S. haixigobicum sp. nov. Qhu-G9. In addition, antiSMASH revealed a large number of gene clusters for the biosynthesis of known and unknown secondary metabolites in the Qhu-G9 genome. [Conclusion] Qhu-G9 isolated from Gobi soil of the QTP is a novel Streptomyces species and has great potential for the production of active secondary metabolites.

Key words:Qinghai-Tibet Plateau;Gobi;Streptomyces;polyphasic taxonomy;gene clusters for biosynthesis