Abstract
Actinomycete bacteria from marine environments represent a potential source for new antibiotics and anti-tumor drugs. Ten strains belonging to the genus Streptomyces isolated from the marine sponge Antho dichotoma collected at the bottom of the Trondheim fjord (Norway) were screened for antibiotic activity. Since only few isolates proved to be bioactive in the conditions tested, we decided to gain an insight into their biosynthetic potential using genome sequencing and analysis. Draft genomes were analyzed for the presence of secondary metabolite biosynthesis gene clusters (BGCs) using antiSMASH software. BGCs specifying both known and potentially novel secondary metabolites were identified, suggesting that these isolates might be sources for new bioactive compounds. The results of this analysis also implied horizontal transfer of several gene clusters between the studied isolates, which was especially evident for the lantibiotic- and thiopeptide-encoding BGCs. The latter implies the significance of particular secondary metabolites for the adaptation of Streptomyces to the spatially enclosed marine environments such as marine sponges. Two bioactive isolates, one showing activity against both yeast and Bacillus subtilis, and one only against yeast were analyzed in details, leading to the identification of cycloheximide, linearmycins, and echinomycins that are presumably responsible for the observed bioactivities.
Highlights
Streptomyces are Gram-positive GC rich bacteria of the order Actinomycetales that are ubiquitous in nature and can be isolated from a variety of sources, including terrestrial, as well as marine habitats (Goodfellow et al, 2018; Subramani and Sipkema, 2019)
Recent comparative genomics-based studies of Streptomyces and other actinomycete bacteria revealed that representatives of the same species isolated from different environments have different sets of secondary metabolite biosynthesis gene clusters (BGCs) (Ian et al, 2014; Ziemert et al, 2014)
A sample of the marine sponge collected at the Tautra underwater ridge in the Trondheim fjord (Norway) and classified as A. dichotoma was used to isolate actinomycete bacteria
Summary
Streptomyces are Gram-positive GC rich bacteria of the order Actinomycetales that are ubiquitous in nature and can be isolated from a variety of sources, including terrestrial (soil, insects, animals and plants), as well as marine (sediments, fish, corals and sponges) habitats (Goodfellow et al, 2018; Subramani and Sipkema, 2019). These bacteria remain of significant interest in terms of discovery of biologically active secondary metabolites that can potentially be developed into human medicines such as antimicrobial and anticancer agents, immunosuppressants etc. It is worth mentioning that some Streptomyces spp. harbor giant linear plasmids (GLPs) that are self-transmissible, frequently carry several BGCs (Kinashi, 2011) and can be involved in the transfer of these BGCs to other bacteria, in particular actinomycetes
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