title: Mechanistic antimicrobial approach of extracellularly synthesized silver nanoparticles against gram positive and gram negative bacteria.
abstract: The development of eco-friendly and reliable processes for the synthesis of nanoparticles has attracted considerable interest in nanotechnology. In this study, an extracellular enzyme system of a newly isolated microorganism, Exiguobacterium sp. KNU1, was used for the reduction of AgNO₃ solutions to silver nanoparticles (AgNPs). The extracellularly biosynthesized AgNPs were characterized by UV-vis spectroscopy, Fourier transform infra-red spectroscopy and transmission electron microscopy. The AgNPs were approximately 30 nm (range 5-50 nm) in size, well-dispersed and spherical. The AgNPs were evaluated for their antimicrobial effects on different gram negative and gram positive bacteria using the minimum inhibitory concentration method. Reasonable antimicrobial activity against Salmonella typhimurium, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus was observed. The morphological changes occurred in all the microorganisms tested. In particular, E. coli exhibited DNA fragmentation after being treated with the AgNPs. Finally, the mechanism for their bactericidal activity was proposed according to the results of scanning electron microscopy and single cell gel electrophoresis.
authors.affiliation: Department of Environmental Engineering, Kyunpook National University, 80 Daehak-ro, Buk-gu, Daegu 702-701, Republic of Korea.
authors.forename: Dhawal P
authors.initials: DP
authors.lastname: Tamboli
authors.forename: Dae Sung
authors.initials: DS
authors.lastname: Lee
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D020552:Comet Assay; D004275:DNA, Ribosomal / Q000737:chemistry; D004926:Escherichia coli / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology; D010802:Phylogeny; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D012486:Salmonella typhimurium / Q000187:drug effects; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013211:Staphylococcus aureus / Q000187:drug effects; D020349:Surface Plasmon Resonance; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D004275:DNA, Ribosomal; D012834:Silver
keywords: Antimicrobial activity; Exiguobacterium sp. KNU1; Scanning electron microscopy; Silver nanoparticles; Single cell gel electrophoresis