Toxicity and Unusual Biological Behavior of Nanosilver on Gram Positive and Negative Bacteria Assayed by Microtiter-Plate

The microtiter-plate test is an important indicator for the pathogenicity of bacteria and the most frequently used techniques for quantifying growth, biofilm formation and respiration assay. The purpose of the present study was to develop a microtiter-plate test, as a quantitative assay, for nanosilver toxicity. It is also superior to the standard microtiter-plate test because it enables indirect measuring of bacteria attached both to the bottom and to the walls of the wells in present of nanosilver. It was surprising that 0.2 ppm of nanosilver promote the formation of biofilm while above this concentration inhibit the biofilm formation by different Gram positive and negative bacteria.