青藏高原戈壁生境中一株链霉菌新种Streptomyces haixigobicum sp.nov.Qhu-G9的多相分类学鉴定及其次级代谢产物的基因组挖掘

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

【背景】青藏高原极端生境具有丰富的微生物资源,同时也是微生物药物的重要来源,但是大量微生物新资源尚待开发利用。【目的】对从青藏高原戈壁土壤中分离得到的一株链霉菌Qhu-G9进行多相分类鉴定及次级代谢产物生物合成潜力分析。【方法】通过16S rRNA基因扩增、测序和系统发育分析,结合形态、生理生化、细胞化学组分及基因组测序等多相分类特征,确定链霉菌Qhu-G9的分类地位。【结果】Qhu-G9与链霉菌Streptomyces dioscori A217T和Streptomyces auranttiiacus NBRC 13017T相似度最高,均为99.22%,结合形态观察,说明该菌是一株链霉菌。基于16S rRNA基因序列构建的系统发育树显示Qhu-G9独立成支,并且其生理生化和细胞化学成分特征与最相似模式菌存在较大差异。通过基因组测序评估了与最相似模式菌的数字DNA-DNA杂交值(digital DNA-DNA hybridization,dDDH)和平均核苷酸一致性(average nucleotide identity,ANI),发现Qhu-G9与最相似菌S.auranttiiacus NBRC 13017T的dDDH与ANI值最高,分别为36.65%和88.21%,但是均低于判定新菌的阈值,进一步表明Qhu-G9为一株链霉菌属新种,并命名为Streptomyces haixigobicum sp.nov.Qhu-G9。此外,通过antiSMASH分析发现Qhu-G9基因组中存在大量编码已知和未知次级代谢产物的生物合成基因簇。【结论】从青藏高原戈壁土壤中分离得到的Qhu-G9是一株链霉菌新种,并且具有进一步挖掘活性次级代谢产物的潜力。

[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 A217T and S.auranttiiacus NBRC 13017T,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 13017T,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.