TY - JOUR AU - El-Zahed, Mohamed M. AU - Abou-Dobara, M. I. AU - El-Sayed, Ahmed K.A. AU - Baka, Zakaria A. M. PY - 2022/06/03 Y2 - 2024/03/29 TI - Ag/SiO2 nanocomposite mediated by Escherichia coli D8 and their antimicrobial potential JF - Nova Biotechnologica et Chimica JA - Nova Biotechnol. Chim. VL - 21 IS - 1 SE - Research Articles DO - 10.36547/nbc.1023 UR - https://journals.scicell.org/index.php/NBC/article/view/1023 SP - e1023 AB - <p>Silica (SiO<sub>2</sub>) has a fundamental role in the recuperation of plants in response to environmental stresses, besides the induction of resistance against plant diseases. Silver nanoparticles (AgNPs) have a superior antimicrobial activity. The combination between SiO<sub>2</sub> and AgNPs is a promising approach due to their antimicrobial activity, biological activity, low toxicity, and high stability of the produced nanocomposite. The current study postulated a green method for silver/silica nanocomposite (Ag/SiO<sub>2</sub>NC) synthesis at room temperature using the crude metabolites of <em>Escherichia coli</em> D8 (MF062579) strain in the presence of sunlight. UV-Vis spectrophotometry, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) analyses have characterized the biosynthesized nanocomposite. TEM study of Ag/SiO<sub>2</sub>NC showed an average particle size of ~32 – 48 nm whereas AgNPs showed a mean size of 18 – 24 nm. The negative charged Ag/SiO<sub>2</sub>NC (-31.0 mV) showed potent antimicrobial activity against <em>Bacillus cereus</em> ATCC6633, <em>Klebsiella pneumoniae</em> ATCC33495, <em>Staphylococcus </em>aureus (ATCC25923), <em>E. coli</em> (ATCC25922), <em>Candida albicans</em> (ATCC10231), and <em>Botrytis cinerea</em> (Pers: Fr.). The minimum inhibitory concentration (MIC) test showed a dose-dependent manner of Ag/SiO<sub>2</sub>NC antimicrobial action. MIC values of Ag/SiO<sub>2</sub>NC against the tested pathogens exhibited 125 and 6.25 μg.mL<sup>-1</sup> as antibacterial and antifungal agents, respectively. TEM micrographs showed changes in the pathogens treated with Ag/SiO<sub>2</sub>NC including wrinkling, damage, and rupture of the bacterial cell membrane. In addition, the formation of a mucilage matrix connecting the hyphal cells, the appearance of big vacuoles and lipid droplets with severe leakage of cytoplasmic contents of the treated <em>B. cinerea</em> were also recorded.</p> ER -