Major purpose of this study was to explore an alternative and simple method for silver and gold nanoparticles bio-production by Escherichia coli. In the previous (routine) technique for nanoparticles bio-production, after culturing the bacteria, the bacterial culture supernatant was treated with aqueous solutions of silver nitrate and chloroauric acid ions. To perform bio-synthesis of silver and gold nanoparticles by the alternative method, unlike the routine one, the bacteria were subjected to the toxic metal ions at their MICs (minimal inhibitory concentration) immediate after inoculation to the medium. Bio-production of nanoparticles by these two methods was monitored through visible spectrophotometry, transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The results showed that silver and gold nanoparticles were produced by both types of the routine and alternative techniques but the rate of bio-production was relatively more by the alternative one. Moreover, this type of bio-production is simpler, faster and cleaner than the previous one.