Investigating Lemna minor and microorganisms for the phytoremediation of nanosilver and microplastics

Due to improper disposal of materials, the amount of pollution that enters waterways has greatly increased. Pollutants that can escape into waterways include microplastics and nanosilver - which are used in protective equipment and disinfectants, respectively. Phytoremediation, a method of using plants to remove pollutants from the environment, has shown great potential for remediating such contaminated aquatic environments. In addition, bacteria that promote plant growth have been shown to alleviate stress from plants and make biofilms that can capture small particles. Here, we employed Lemna minor, an aquatic floating plant, in combination with three plant growth-promoting bacteria to see which combination could effectively remove more pollutants from a simulated environment. We measured the pollutant-removal efficiency of L. minor, chlorophyll content, biofilm efficiency, and water toxicity. The ability of L. minor to accumulate nanosilver and microplastics increased significantly with the addition of bacteria. The bacteria with the highest biofilm production, measured through crystal violet staining, was associated with an increase in the amount of pollutants removed. When L. minor was exposed to just the pollutants, chlorophyll content significantly decreased from 4.17mg/mL to as low as 2.86 mg/mL; however, with the addition of the bacteria, chlorophyll increased to a point where there was not significant damage. When exposed to the initial and post-remediation concentrations of nanosilver particles, the negative impacts on zebrafish embryos were reduced. These forms of bacteria-assisted phytoremediation provide insight into how treatment plants can effectively remove pollutants from wastewater with the addition of bacteria.