Synthesis of Bioactive Silver Nanoparticles Using New Bacterial Strains from an Antarctic Consortium.

In this study, we report on the synthesis of silver nanoparticles (AgNPs) achieved by using three bacterial strains , and as reducing and capping agents, newly isolated from a consortium associated with the Antarctic marine ciliate . After incubation of these bacteria with a 1 mM solution of AgNO at 22 °C, AgNPs were synthesized within 24 h. Unlike and , the reduction of Ag from AgNO into Ag has never been reported for a strain. The maximum absorbances of these AgNPs in the UV-Vis spectra were in the range of 404 nm and 406 nm. EDAX spectra showed strong signals from the Ag atom and medium signals from C, N and O due to capping protein emissions. TEM analysis showed that the NPs were spherical and rod-shaped, with sizes in the range of 20 to 50 nm, and they were clustered, even though not in contact with one another. Besides aggregation, all the AgNPs showed significant antimicrobial activity. This biosynthesis may play a dual role: detoxification of AgNO and pathogen protection against both the bacterium and ciliate. Biosynthetic AgNPs also represent a promising alternative to conventional antibiotics against common nosocomial pathogens.