The impacts of aluminum and zirconium nano-oxides on planktonic and biofilm bacteria

Nanoparticles are molecules, whose dimensions are below 100 nm; they are of colloidal particle size and are often smaller than eukaryotic cells and bacteria. Their increasingly common application might cause their release into sewage and the induction of toxic reactions, among others, in micro-organisms participating in wastewater treatment. The aim of this study was to compare the ecotoxicity of commercial nanoparticles of aluminum oxides and zirconium oxides, in relation to two bacterial strains Pseudomonas putida and Aeromonas hydrophila. These bacteria have an ability to form biofilms, as they are present in planktons and participate in wastewater treatment. The study also includes the assessment of aluminum oxide (Al2O3) and zirconium oxides' (ZrO2) ecotoxicity in order to compare their harmfulness with the nanoparticular form. It has been found that aluminum and zirconium nano-oxides were more harmful to bacteria compared to aluminum and zirconium oxides. Biofilm-forming bacteria were more resistant than planktonic bacteria to the influence of both types of compounds. Aluminum nano-oxide proved to be more toxic than zirconium nano-oxide in relation to both species of bacteria. Nanoparticles appeared to be less toxic towards bacteria with EPS. A. hydrophila strain showed lower sensitivity than P. putida to the studied nanoparticles.