Abstract
Nanosilver is currently the most developed and commercialised antimicrobial nanomaterials. With proven efficacyagainst a broad spectrum of microorganisms, companies are now adding nanosilver as core antimicrobialingredients in medical and personal care products, household appliances, as dietary supplements and even in babyproducts, just to name a few. The increasing use of nanosilver has raised global concerns with regard to the potentialdevelopment of resistant microorganisms toward these nanoparticles. Here we report for the first time the naturalability of the near ubiquitously-occurring Bacillus spp. to adapt to nanosilver cytotoxicity upon prolonged exposure(Gunawan et al., 2013). The combined adaptive effects of nanosilver resistance and enhanced extent of growth leadto the ultimate domination of the resistant bacteria in the microbiota, to which nanosilver is continuously applied.Importantly, we found that the adaptive effects are stable, in other words the effects are still present even followingdiscontinuation of the nanosilver exposure. The observations of adaptation and ultimate domination of Bacillusspp. are relevant to wider microbiotas, presenting consequences of extensive microorganism exposure, includingthose that dwell in the human body, to bioavailable silver derived from the products. The discovery is an alert to thecommon perception of nanosilver as a risk-free antimicrobial.