Biosynthesis, Characterization, Optimization of Silver Nanoparticles from Marine S. griseoflavus and Their Role in Improving Antibiotic Susceptibility of Multidrug Resistance Pathogenic Fungi

Muneera Al-Otaibi, Bahig El-Deeb, Nasser Mostafa

Abstract


Green synthesis of silver nanoparticles using marine microorganisms has gained profound interest because of their potential to synthesize nanoparticles of various size, shape and morphology. In the present investigate, 25 silver resistant bacterial isolates were isolated from different sites of red sea cost at  Jeddah city, , bacterial strain BM3 was selected on the basis of its ability to produce stable extracellular silver nanoparticles ( AgNPs). Biochemical and Molecular characterization of this isolate indicated that BM3 strain is belonged to Streptomyces  and identified as S. griseoflavus. The biosynthesis of AgNPs was monitored by UV–Visible spectrum that showed surface plasmon resonance (SPR) peak at 420 nm. Further characterization of synthesized AgNPs was carried out using the XRD, TEM and FTIR spectroscopy. TEM and XRD analysis revealed that the AgNPs synthesized by MB was spherical in shape with a size range of 5-45. nm FTIR confirmed the presence of proteins as the stabilizing agent surrounding the nanoparticles.Optimization of silver nanoparticles synthesis has been studied and the results demonstrated that the biosynthesis of AgNPs by bacterial supernatant increased with the  increasing of  the temperature, pH  and Ag+ ions concentration. The synthesized AgNPs and their combination with different commercial antibiotic were tested against C. albicans and C.krusei.All tested antibiotics showed synergistic inhibition against growth of the pathogenic bacteria. The biocide actions of AgNPs studied using SEM. The results showed damage in membrane and some pits that have been created cause inter cellular components leakage and finally cell death .

UV-Vis absorption spectra of AgNPs alone, each antibiotic alone, and AgNPs-antibiotic combinations were studied . The results clearly point out that the synergistic effect of AgNPs-antibiotic combination against pathogenic is mediated by complexes that are produced from the interaction between AgNPs and the antibiotics, instead of individual or additive action of AgNPs or antibiotic .In other words, the pathogenic cells are killed more effectively by “AgNPs-antibiotic complexes” .However, the nature of the interaction between the AgNPs and the antibiotics needs further investigation.


Keywords


Marine bacteria; Antifungal activity; Optimization of silver nanoparticles; Biochemical and Molecular characterization.

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