Abstract
A novel actinobacterium, strain HNM0039T, 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 Streptomyces. Based on the 16S rRNA gene sequence analysis, strain HNM0039T was closely related to Streptomyces wuyuanensis CGMCC 4.7042T (99.38%) and Streptomyces spongiicola HNM0071T (99.05%). The organism formed a well-delineated subclade with S. wuyuanensis CGMCC 4.7042T and S. spongiicola HNM0071T in the Streptomyces 16S rRNA gene tree. Multi-locus sequence analysis (MLSA) based on five house-keeping gene alleles (atpD, gyrB, rpoB, recA, trpB) further confirmed their relationship. DNA–DNA relatedness between strain HNM0039T and its closest type strains, namely S. wuyuanensis CGMCC 4.7042T and S. spongiicola HNM0071T, were 46.5 and 45.1%, respectively. The average nucleotide identity (ANI) between strain HNM0039T and its two neighbor strains were 89.65 and 91.44%, respectively. The complete genome size of strain HNM0039T 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 HNM0039T. Among them, the tirandamycin biosynthetic gene cluster has been characterized completely. The crude extract of strain HNM0039T exhibited potent antibacterial activity against Streptococcus agalactiae 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 HNM0039T represents a novel species of the genus Streptomyces whose name was proposed as Streptomyces tirandamycinicus sp. nov. The type strain is HNM0039T (= CCTCC AA 2018045T = KCTC 49236T).
Highlights
During our ongoing efforts to discover antibacterial agents from marine sponge-associated actinomycetes, a novel actinobacterial strain HNM0039T isolated from a marine sponge sample that was collected at the coast of Wenchang, Hainan island of China, was recognized as a novel species of the genus Streptomyces through a polyphasic approach and its name was proposed as Streptomyces tirandamycinicus sp. nov. in the present study
Strain HNM0039T shared highest 16S rRNA gene sequence similarities to S. wuyuanensis CGMCC 4.7042T (99.38%) and S. spongiicola HNM0071T (99.05%), and less than 99% sequence similarities to other type strains of the genus Streptomyces
The close relationships between strain HNM0039T with S. spongiicola HNM0071T and S. wuyuanensis CGMCC 4.7042T were further confirmed by the multi-locus sequence analysis (MLSA) tree (Figure 2)
Summary
Marine sponge-associated actinomycetes have gained considerable attention during the last decade as a vast source of novel natural products (NPs) with variety of bioactivities, including anti-biofilm (Balasubramanian et al, 2017, 2018), anti-chlamydial (Reimer et al, 2015; Cheng et al, 2016), antimicrobial (El-Gendy and El-Bondkly, 2010; Elsayed et al, 2018), antioxidant (Grkovic et al, 2014; Cheng et al, 2016), antiparasitic (Elsayed et al, 2017), antitumor (Yi-Lei et al, 2014; Yan et al, 2017), and immunomodulatory (Tabares et al, 2011) activities. The complete genome information of strain HNM0039T was analyzed to obtain further understanding on its antibacterial potential at genomic levels
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