Elucidation of biogenic silver nanoparticles susceptibility towards Escherichia coli: an investigation on the antimicrobial mechanism.

Elucidation of the role of silver nanoparticles (AgNPs) in combating bacterial infection is important for the development of new antimicrobial compounds. In this study, several key factors underlying biological effects of biogenic AgNPs were investigated on recombinant Escherichia coli (XL1-Blue) which contains a reporter gene encoding β-galactosidase enzyme. Biogenic AgNPs were prepared from the tea decoction. Cytotoxicity effects were profound on the bacteria tested by the synthesised NPs. The β-galactosidase activity of the released intracellular proteins in the supernatant of E. coli was used as a measure of membrane damage and cellular leakage. Occurrence of a significant amount of β-galactosiadase activity in the supernatant of treated cells clearly demonstrated the formation of holes in the bacterial membrane. Scanning electron microscope pictures visibly indicated destruction of the membrane of the bacteria, which further confirmed membrane damage. The synthesised NPs caused damage of E. coli genomic DNA in a dose dependent manner.