Antibacterial and antioxidant activities of Streptomyces sp. strain FR7 isolated from forest soil

• Published in: Letters in applied microbiology Vol. 76; no. 4
• Main Authors: Weslati, Imen, Simões, Luara, Teixeira, Ana, Parpot, Pier, Raies, Aly, Oliveira, Rui
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 03.04.2023
• Subjects: Acetic acid; Actinomycetes; Anti-Bacterial Agents - metabolism; Anti-Infective Agents - metabolism; Antiinfectives and antibacterials; Antimicrobial activity; Antimicrobial agents; Antioxidants; Antioxidants - metabolism; Antioxidants - pharmacology; Biological activity; Ethyl acetate; Flow cytometry; Forest soils; Forests; Gene sequencing; Hydrogen peroxide; Hydrogen Peroxide - metabolism; Metabolites; Microbial Sensitivity Tests; Minimum inhibitory concentration; Oxidative stress; Polyketides; Scavenging; Secondary metabolites; Soil; Strains (organisms); Streptomyces; Streptomyces - metabolism; soil; actinomycetes; antimicrobials; polyketides; Streptomycetes; antioxidants
• ISSN: 1472-765X; 0266-8254; 1472-765X
• DOI: 10.1093/lambio/ovad036

Actinomycetes produce secondary metabolites with many bioactivities such as antimicrobial, which can be useful as alternatives against resistant bacterial strains. Therefore, the screening of new habitats is likely to provide new strains with high potential. In this work, the antimicrobial capacity was used to select Streptomyces sp. strains isolated from Raf Raf forest (Tunisia). From the strain displaying higher activity, FR7, an ethyl acetate extract was prepared under optimized culturing conditions (10 days at 30°C in ISP2 medium with initial pH 8), showing significant antimicrobial activity against Micrococcus luteus and Staphylococcus aureus (MIC = 5 μg ml−1), and Listeria monocytogenes and Pseudomonas aeruginosa (MIC = 20 μg ml−1). The extract displayed strong DPPH radical scavenging activity (IC50 = 1.3 μg ml−1) and protection of yeast cells from H2O2-induced oxidative stress determined by flow cytometry with dichlorofluorescein diacetate. The crude extract showed the presence of polyketides, with methylsalicylic acid as moiety, a large and diverse group of secondary metabolites with a wide range of bioactivities, including antioxidant and antibacterial. Based on 16S RNA gene sequences, strain FR7 was identified as belonging to genus Streptomyces with high resemblance to S. iakyrus. Streptomyces sp. FR7 has great potential as a source of antibacterial and antioxidant metabolites.