Synthesis of nanoparticles using various biological sources, have shown that these nanoparticles possess antimicrobial activity. They have unique properties which help in molecular diagnosis, in therapies, as well as in devices that are used in several medical procedures. In our previous studies, AgNPs were synthesized from filtered buttermilk and these AgNPs possessed antibacterial activity against both Gram positive and Gram negative organisms but Gram negative were more susceptible. In this research our main focus was on Mode of action of antimicrobial activity of these AgNPs synthesized from filtered buttermilk, whether it causes DNA fragmentation or causes cell permeability. DNA isolated from the AgNP treated cells did show DNA fragmentation. The antimicrobial action of silver nanoparticles may be due the cell membrane damage also, as we observed the leakage of the proteins and DNA in the broth of the cells treated with AgNPs. This leakage may lead to the loss of many important enzymes which can cause bacterial death. Also, our results point out the hamper of normal signal transduction required for survival of the bacteria.

Key words: Silver Nanoparticles (AgNPs), filtered buttermilk, DNA fragmentation, cell permeability, antimicrobial activity