Biological production and assessment of the antibacterial activity of gold nanoaprticles

In addition to safety, nanoparticles produced via biological methods show antimicrobial activity against human pathogens. This study was aimed to isolation and identification of intracellular and extracellular gold nanoparticle producing strains from soil and to investigate the antimicrobial effects of the produced nanoparticles on 10 common bacterial pathogens. In this study, after isolation of bacteria from the soil and production of the gold nanaoparticles by their supernatants and their pure cells, the bio-production was confirmed through visible spectrophotometry, transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The nanoparticle producing stains were identified based on gene amplification by PCR and gene sequencing. Finally, the antibacterial properties of the produced gold nanoaprticles against 10 pathogenic bacteria was assessed by well diffusion method. Results showed that 38 strains had ability to produce extracellular gold nanoparticles. Among them 16 strains had ability to produce intracellular gold nanoparticles as well. TEM images of the gold nanoparticles showed sizes less than 100 nm and the XRD patterns confirmed the crystalline structure of the gold nanoparticles. Three bacterial strains, Bacillus mojavensis, Bacillus subtilis and Bacillus vallismortis, showed higher productivity. Antibacterial tests showed that the extracellular gold nanoaprticles had better activity against pathogenic bacterial strains than the intracellular produced ones. Production of gold nanoparticles was performed by biological method. This nanoparticles showed a same antibacterial activity against both tested gram positive and negative bacteria.