AUTHOR=Huang Xiaolong , Kong Fandong , Zhou Shuangqing , Huang Dongyi , Zheng Jiping , Zhu Weiming 

TITLE=Streptomyces tirandamycinicus sp. nov., a Novel Marine Sponge-Derived Actinobacterium With Antibacterial Potential Against Streptococcus agalactiae

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00482

DOI=10.3389/fmicb.2019.00482

ISSN=1664-302X

ABSTRACT=<p>A novel actinobacterium, strain HNM0039<sup>T</sup>, was isolated from a marine sponge sample collected at the coast of Wenchang, Hainan, China and its polyphasic taxonomy was studied. The isolate had morphological and chemical characteristics consistent with the genus <italic>Streptomyces</italic>. Based on the 16S rRNA gene sequence analysis, strain HNM0039<sup>T</sup> was closely related to <italic>Streptomyces wuyuanensis</italic> CGMCC 4.7042<sup>T</sup> (99.38%) and <italic>Streptomyces spongiicola</italic> HNM0071<sup>T</sup> (99.05%). The organism formed a well-delineated subclade with <italic>S. wuyuanensis</italic> CGMCC 4.7042<sup>T</sup> and <italic>S. spongiicola</italic> HNM0071<sup>T</sup> in the <italic>Streptomyces</italic> 16S rRNA gene tree. Multi-locus sequence analysis (MLSA) based on five house-keeping gene alleles (<italic>atp</italic>D, gyrB, rpoB, recA, trpB) further confirmed their relationship. DNA–DNA relatedness between strain HNM0039<sup>T</sup> and its closest type strains, namely <italic>S. wuyuanensis</italic> CGMCC 4.7042<sup>T</sup> and <italic>S. spongiicola</italic> HNM0071<sup>T</sup>, were 46.5 and 45.1%, respectively. The average nucleotide identity (ANI) between strain HNM0039<sup>T</sup> and its two neighbor strains were 89.65 and 91.44%, respectively. The complete genome size of strain HNM0039<sup>T</sup> was 7.2 Mbp, comprising 6226 predicted genes with DNA G+C content of 72.46 mol%. Thirty-one putative secondary metabolite biosynthetic gene clusters were also predicted in the genome of strain HNM0039<sup>T</sup>. Among them, the tirandamycin biosynthetic gene cluster has been characterized completely. The crude extract of strain HNM0039<sup>T</sup> exhibited potent antibacterial activity against <italic>Streptococcus agalactiae</italic> in Nile tilapia. And tirandamycins A and B were further identified as the active components with MIC values of 2.52 and 2.55 μg/ml, respectively. Based on genotypic and phenotypic characteristics, it is concluded that strain HNM0039<sup>T</sup> represents a novel species of the genus <italic>Streptomyces</italic> whose name was proposed as <italic>Streptomyces tirandamycinicus</italic> sp. nov. The type strain is HNM0039<sup>T</sup> (= CCTCC AA 2018045<sup>T</sup> = KCTC 49236<sup>T</sup>).</p>