Antimicrobial activities of silver nanoparticles synthesized from Lycopersicon esculentum extract

Background: It has been known for quite some time now that silver nanoparticles (AgNP) can inhibit microbial growth and even kill microbes. Our investigation reports the antimicrobial activity of AgNP against a model bacterium, Escherichia coli. Methods: The aqueous extract of Lycopersicon esculentum (red tomato) was used for the rapid synthesis of AgNP, which is very simple and eco-friendly in nature. The UV-visible spectroscopy technique was employed to establish the formation of AgNP. Results: The transmission electron microscopic images showed that the particles were of mostly spherical shape. For the bacteriological tests, the microorganism E. coli was inoculated on Luria broth (LB) agar plate in the presence of varied amounts of AgNP. The antibacterial activity was obvious from the zone of inhibition. At concentration 20 μg/ml and above, the AgNP showed a clear zone of inhibition and the minimum inhibitory concentration of AgNP to E. coli was 50 μg/ml. Growth rates and bacterial concentrations were determined by measuring optical density at 600 nm at different time points. Conclusions: From the slope of the bacterial growth curve, it has been concluded that the nanoparticles are bacteriostatic at low concentration and bactericidal at high concentration. So these nanoparticles are believed to act as preventive for bacterial contamination.