Aims: Actinomyces are dominant soil microflora with potent activity for production of several enzymes and metabolites. In order to increase their survival in the environment these bacteria detoxify the metal ions and consequently produce the nanoparticles. The present study was undertaken to isolate Actinomyces strains from soil samples and their evaluation for the production of silver nanoparticles with antimicrobial property. Methodology and results: Two hundred soil samples were collected and subjected to isolation and identification (based on16SrRNA gene sequencing) of silver nanoparticles producing Actinomyces. The silver nanoparticles produced by Actinomyces were confirmed by UV-visible spectral analysis, scanning electron microscope (SEM) and Inductively Coupled Plasma (ICP). Furthermore, antimicrobial property of silver nanoparticles was assessed against pathogenic microorganisms viz., Staphylococcus aureus (PTCC 1431), Acinetobacter baumannii (PTCC 19606), Bacillus cereus (PTCC 1816), Escherichia coli (PTCC 1397), Salmonella typhi (PTCC 1609), Pseudomonas aeruginosa (PTCC 1707), Aspergillus niger (PTCC 5010) and Candida albicans (PTCC 5072). Of 48 Actinomyces isolated, 26 strains could produce silver nanoparticles and three of which showed potent activity for production of silver nanoparticles. Molecular identification of these strains exhibited detection of Actinomyces amycolicicoccus subflavus, Streptomyces flavoviridis and Streptomyces lateritius. The results obtained from characterization of the biosynthesis silver nanoparticles illustrated that their shapes and sizes were spindle and spherical and 47-103 nm respectively. However, the antimicrobial effect of silver nanoparticles against the pathogenic microorganisms was varied. Yet S. typhi followed by P. aeruginosa, were more sensitive and A. baumannii was relatively less sensitive. In addition, spherical shape with small average size relatively showed more antimicrobial property. Conclusion, significance and impact of study: Soil Actinomyces could produce silver nanoparticles and these particles have antimicrobial effect. In addition, the antimicrobial effect of silver nanoparticles, not only because of their chemical property (such as formation of free radical) but also depended on their shapes and sizes.
Actinomyces