TiO₂ nanoparticles affect the bacterial community structure and Eisenia fetida (Savigny, 1826) in an arable soil

The amount of nanoparticles (NP), such as TiO₂, has increased substantially in the environment. It is still largely unknown, however, how NP might interact with earthworms and organic material and how this might affect the bacterial community structure and their functionality. Therefore, an arable soil was amended with TiO₂ NP at 0, 150 or 300 mg kg^-1 and subjected to different treatments. Treatments were soil amended with ten earthworms (Eisenia fetida (Savigny, 1826)) with fully developed clitellum and an average fresh mass of 0.5 to 500 g dry soil, 1.75 g tyndallized Quaker^® oat seeds Avena sativa (L.) kg^-1, or earthworms plus oat seeds, or left unamended. The bacterial community structure was monitored throughout the incubation period. The bacterial community in the unamended soil changed over time and application of oats, earthworm and a combination of both even further, with the largest change found in the latter. Application of NP to the unamended soil and the earthworm-amended soil altered the bacterial community, but combining it by adding oats negated that effect. It was found that the application of organic material, that is, oats, reduced the effect of the NP applied to soil. However, as the organic material applied was mineralized by the soil microorganisms, the effect of NP increased again over time.