Impact of manufactured TiO₂ nanoparticles on planktonic and sessile bacterial communities

In the present study, we conducted a 2 week microcosm experiment with a natural freshwater bacterial community to assess the effects of titanium dioxide nanoparticles (TiO₂-NPs) at various concentrations (0, 1, 10 and 100 mg/L) on planktonic and sessile bacteria under dark conditions. Results showed an increase of planktonic bacterial abundance at the highest TiO₂-NP concentration, concomitant with a decrease from that of sessile bacteria. Bacterial assemblages were most affected by the 100 mg/L TiO₂-NP exposure and overall diversity was found to be lower for planktonic bacteria and higher for sessile bacteria at this concentration. In both compartments, a 100 mg/L TiO₂-NPs exposure induced a decrease in the ratio between the Betaproteobacteria and Bacteroidetes. For planktonic communities, a decrease of Comamonadaceae was observed concomitant with an increase of Oxalobacteraceae and Cytophagaceae (especially Emticicia). For sessile communities, results showed a strong decrease of Betaproteobacteria and particularly of Comamonadaceae. - Highlights: • Microcosm experiments with natural water exposed to TiO₂-NPs. • Toxicity of TiO₂-NPs assessed on both planktonic and sessile bacteria. • Effects on bacterial community structure and diversity. • Shift occurs in the Betaproteobacteria/Bacteroidetes repartition in communities. - TiO₂-NPs increase abundance of planktonic bacteria, decrease that of sessile bacteria, and affect diversity and structure of communities in both cases