By using cell culture supernatant, synthesis rate of some bacterial strains such as Enterobacter cloacae, E. coli and K. Pneumonia . The AgNPs obtained were formed within 5 minutes of silver ions (Ag + ) contacting the cell filtrate, it is reported that the nitro reductant enzymes are responsible for the reduction of silver ion to metallic silver which is accumulated on the cell wall . A study reported that visible-light emission can significantly enhance the synthesis of AgNPs of size 1-6 nm by using culture supernatant of K. pneumonia . The obtained AgNPs can be used in biosensor, drug delivery and as antimicrobial agent . However, the process is slow as compared to the other biological methods used to synthesize silver nanoparticles . The examples of different bacterial strains used in the synthesis of AgNPs are summarized in Table .