BMC Microbiology (Apr 2022)

Synthesis of silver nanoparticles with high efficiency and stability by culture supernatant of Bacillus ROM6 isolated from Zarshouran gold mine and evaluating its antibacterial effects

  • Rostampour Esmail,
  • Alihosseini Afshar,
  • Milani Morteza,
  • Akbarzadeh Abolfazl,
  • Ebrahim Akhondi

DOI
https://doi.org/10.1186/s12866-022-02490-5
Journal volume & issue
Vol. 22, no. 1
pp. 1 – 10

Abstract

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Abstract Background The use of bacteria to synthesize nanoparticles as an environment-friendly method has recently been considered by researchers. Bacteria residing in different mines have shown high potential in the synthesis of metal nanoparticles due to their compatibility with the environment. The aim of this study was to evaluate the ability of Zarshouran gold mine bacteria to synthesize silver nanoparticles and their antibacterial activity. Methods After isolation of mine bacteria and several screening steps, silver ion tolerant bacteria that were able to synthesize extracellular silver nanoparticles were isolated and the most suitable isolate was selected and sequenced. The characteristics, stability, and production efficiency of silver nanoparticles were evaluated using UV–vis spectrophotometry, DLS, TEM, FTIR, and X-ray diffraction analysis. Finally, the antibacterial effect of silver nanoparticles against pathogenic bacteria was investigated. Results Among the eight silver-tolerant bacteria, isolate No. 6 had high antibacterial activity and high potential in the synthesis and stabilization of silver nanoparticles. Therefore, this isolate was selected for the next experiments. The results of 16S rDNA sequencing showed that this isolate is related to Bacillus pumilus. We registered in the NCBI Bank called ROM6 with access number MW440543. The DLS and TEM analysis showed that silver nanoparticles produced by this isolate were most spherical with a size of less than 25 nm and were stable for at least 180 days. The efficiency at concentrations less than 0.9 g/l silver nitrate was over 90% and the minimum inhibition concentration of nanoparticles was determined against S. aureus, E. coli, P. aeruginosa, and A. baumannii ranging from 1.4 to 5.6 µg/ml. Conclusion We found that the bacteria residing in the gold mine have a high capacity for the synthesis of spherical and high stable silver nanoparticles with a strong antibacterial effect.

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