Unique secondary metabolites of a Streptomyces strain isolated from extreme salty wetland show antioxidant and antibacterial activities

Aims To identify and assess the biological activities of the crude extract of a Streptomyces isolate from a salty wetland, an extreme environment likely to induce secondary metabolism of microorganisms. Methods and Results The crude extract from the isolate Streptomyces lanatus strain AR2 displayed antibacterial activity against Gram-positive bacteria (MICs ranging from 5 to 50 μg ml-1) and antioxidant activity as revealed in DPPH (2,2-diphenyl-1-picrylhydrazyl) assay (IC50 of 0.74 mg ml-1), ferric reducing antioxidant power (IC50 of 1.12 mg ml-1) and metal chelating power (IC50 of 1.84 mg ml-1) assays. Accordingly, the extract attenuated the H2O2-induced oxidative stress in the eukaryotic cell model Saccharomyces cerevisiae, assessed by flow cytometry. The profiling of secondary metabolites by HPLC-PDA-ESI-MS/MS revealed the presence of 17 compounds, some of which reported in Streptomyces for the first time to the best of our knowledge: Genistein-7-O-glucuronide, naringenin-7-O-rutinoside and resveratrol. Conclusions Streptomyces lanatus AR2 produced unique polyketides and phenolic compounds with noticeable bioactivities, allowing adaptation to the extreme environment. Significance and Impact of the Study Sabkhat Seijoumi salty wetland represent a potential niche for Streptomyces yielding useful natural products for biotechnological, pharmaceutical and medical applications. This article is protected by copyright. All rights reserved.The authors are grateful to the ‘Ministere de l’Enseignement Superieur et de la Recherche Scientifique of Tunisia’ and the University of Tunis El Manar for providing financial support. We thank Prof. A. HASSEN of the Laboratory of Treatment and Water Recycling, Centre of Research and Water Technologies (CERTE), Techno park of Borj-Cedria (CERTE, Tunisia) for his technical review and Prof. M. MRABET of the Laboratory of Legumes Centre of Biotechnology of Borj Cedria, Hammam-Lif, Tunisia for his technical assistance in phylogenic analyses. This work is supported by National Funds by FCT—Portuguese Foundation for Science and Technology, under the project UID/AGR/04033/2019.info:eu-repo/semantics/publishedVersio