Photoexcited graphene oxides activate silent viruses in bacteria with dependency on their sizes

Graphene oxides (GOs) have been the focus of recent research with a rapidly expanding range of applications. However, little is known about their influence on bacterial ecosystems. Therefore, we investigated the dependency of the activation of silent viruses inside bacteria, called prophages, on the size of single-layer GOs. Such viruses activated and released into the environment can further infect bacteria, killing them and multiplying, thereby interfering with microbially catalyzed ecosystem functions. We found that photoexcited GOs with a small average sheet area (0.014 and 0.34 μm 2 ) activated prophages, while larger GOs (6.04 μm 2 ) did not show this effect. Owing to their sharp edges, the smaller GOs can cut into the membrane, raise the cellular oxidative stress via photo-generated ROS, and thereby activate prophages. Our work emphasizes an ecotoxicological effect of GOs which was previously overlooked. Smaller graphene oxides can cut into bacteria and induce lysogenic activation via photo-generated singlet oxygen.