Abstract
Lake Mariout is one of the polluted coastal marine ecosystems in Egypt which is considered to be a reservoir of serious effluents from different anthropogenic activities. Such selective pressure enforces indigenous microbial populations to acquire new advantageous themes. Thus, in this study, two Streptomyces strains were screened, from Lake Mariout’s sediment for bioreduction of 5 mM AgNO3. Both strains were identified molecularly; their biochemical and physiological characterization revealed their ability to secrete bioactive metabolites with antagonistic activity. The cultural and incubation conditions influencing AgNPs productivity were evaluated. Subsequently, the physicochemical properties of the biofabricated AgNPs were pursued. UV-Vis spectroscopy detected surface plasmon resonance at range 458–422 nm. XRD indicated crystalline, pure, face-centered cubic AgNPs; EDX demonstrated strong silver signal at 3.5 keV. Besides, FT-IR and TGA analysis unveiled self-stabilization and functionalization of AgNPs by bioorganic molecules. However, electron microscopy micrographs depicted numerous uniform spherical AgNPs (1.17–13.3 nm). Potent bactericidal and fungicide activity were recorded by zone of inhibition assay at 50 μg/mL. Further, the antibiofilm activity was exerted in a dose-dependent manner. Moreover, the conjugation of AgNPs with the crude bioactive metabolites of both bionanofactories ameliorated the antimicrobial potency, reflecting a synergistic efficiency versus examined pathogens (free-living and biofilm).
Highlights
Lake Mariout is one of the major lagoons in Egypt, its shore occupied by aquaculture and fishers
As reported by [39], they produced more than 45% of known pharmaceutical products; they were categorized among nanoparticle producers, occupying a prominent site in both medical and biotechnological sectors
This study sheds light on the biosynthesis of AgNPs via two Streptomycetes sp. strains isolated from Lake Mariout in a simple, less expensive, efficient and eco-friendly approach
Summary
Lake Mariout is one of the major lagoons in Egypt, its shore occupied by aquaculture and fishers. It is located in Alexandria city, with coordinates that lie between latitude 31◦9 11 (N), longitude 29◦53 55 (E); it covers 50 km area with water depth range 0.6–1.5 m [1]. Through three main inflows (El-Qalaa, El-Umum and ElNubariya) and other small outfalls from water treatment plants and the effluent drains from the petrochemical area, the lake receives substantial industrial, agricultural and municipal discharges that degrade the quality of the lake water [2,3]. Several investigations have assessed its water quality by determining several parameters such as eutrophication status, heavy metals content, microbial diversity, salinity and inorganic matter contents as well [1,4,5]. The heavy metals concentration in Lake Mariout sediments seemed to be higher than those recorded in other Egyptian lakes and so it was referred to as the most anthropogenically polluted and eutrophic wetland in the Nile Delta [5]
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