Biogenic synthesis of silver-nanoparticles with the brackish water cyanobacterium Nostoc sphaeroides and assessment of antibacterial activity against urinary tract infecting bacteria

The aim of this study was to isolate a filamentous nitrogen-fixing cyanobacterium Nostoc sphaeroides (NS) from brackish water of Chilika Lake, Odisha coast, and exploration of its use in the biosynthesis of silver-nanoparticles (AgNPs) against the urinary tract-infecting bacterial strains. The synthesized NS-AgNPs were structurally characterized by analytical techniques such as UV-visible-spectrophotometry, FTIR, XRD, SEM and SEM-EDX. The antibacterial efficacy of synthesized AgNPs had remarkable in vitro activities with the MIC value of 50 mg/ml. Moreover, Nostocine A, the inherent bioactive compound of Nostoc sp. was further investigated for molecular docking studies against the targeted bacterial DNA gyrase (Escherichia coli) and the obtained docking score was -7.9 kCal/mol as compared with the standard drug, Ciprofloxacin of a docking score -7.8 kCal/mol. The concordance between molecular docking and experimental results is excellent. Thus, the biogenic-synthesized "N. sphaeroides-AgNPs" would be used as an antibacterial agent in future.