Determination of nanotixicity of functionalized titanium dioxide (TiO2) nanoparticles (NPs) towards Rhizobium etli bacteria in soil

Emerging pollutants such as metal nanoparticles and TiO2 nanoparticles have varying impacts on the survival of nitrogen-fixing bacteria in the soil. The health of the soil can be affected due to the harmful effects of these contaminants on plant-growth-promoting bacteria (PGPB), thereby impacting plant productivity. The produced TiO2 NPs were examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The toxicity of nano-titanium dioxide and the molecular effect of a gene on Rhizobium bacteria isolated from broad bean (Vicia faba L.) roots were studied. B cell receptor (BCR) was used to identify the isolates. To test the bacterial sensitivity to TiO2, four holes were bored into the menthol medium using a 6 mm sterile drill. Titanium NPs were added at different concentrations (1225, 2500, and 5000 ppm) in the well; and after 24 hours, TiO2 had no influence on bacterial growth but there was a high density of actively growing microorganisms. The relative gene expression of the rhizobium isolates (ropA) compared to the housekeeping gene (recA) was then measured. As a result, it was determined that the gene expression activity of the bacteria increased or decreased depending on the titanium concentration. It was concluded that titanium is a good option for increasing the activity and productivity of rhizobium bacteria, provided the appropriate concentration is determined.