Nanoparticles affect the survival of bacteria on leaf surfaces.

The increasing presence of nanomaterial and nanoproducts makes it imperative to learn more about the associated impacts of these materials on human health and the environment. In this study, the effect of the nanomaterial TiO2 on the phyllosphere microbial community was investigated. Analysis results by PCR-denaturing gradient gel electrophoresis revealed a TiO2-induced change in the community structure of microorganisms. An epiphytic bacterium, Bacillus cereus 905, was chosen to study the role of the superoxide dismutase-encoding genes, sodA-1 and sodA-2, and its survival from TiO2 photocatalysis. Our results showed that the expression of sodA-1 and sodA-2 was induced by photocatalytic oxidation, with a higher induction observed in sodA-2. In addition, compared with wild-type B. cereus 905, a reduced bacterial population was observed in a sodA-1 and sodA-2 double deletion mutant strain KOS on a cucumber leaf surface sprayed with TiO2. Because the phyllosphere is considered as one of the major habitats for microorganisms, and substantial areas of the earth are covered with leaves, the results of this work provides information of the potential impact of photocatalytic nanomaterial in the environment.