Elucidating the effect of TiO₂ nanoparticles on mung bean rhizobia via in vitro assay: Influence on growth, morphology, and plant growth promoting traits

Abstract

Titanium dioxide nanoparticles (TiO2 NPs) are among the most commonly used nanomaterials and are most likely to end up in soil. Therefore, it is pertinent to study the interaction of TiO2 NPs with soil microorganisms. The present in vitro broth study evaluates the impacts of low‐dose treatments (0, 1.0, 5.0, 10.0, 20.0, and 40.0 mg L−1) of TiO2 NPs on cell viability, morphology, and plant growth promoting (PGP) traits of rhizobia isolated from mung bean root nodule. Two types of TiO2 NPs, that is, mixture of anatase and rutile, and anatase alone were used in the study. These TiO2 NPs were supplemented in broth along with a multifunctional isolate (Bradyrhizobium sp.) and two reference cultures. The exposure of TiO2 (anatase+rutile) NPs at low concentrations (less than 20.0 mg L−1) enhanced the cell growth, and total soluble protein content, besides improving the phosphate solubilization, Indole‐3‐acetic acid (IAA) production, siderophore, and gibberellic acid production. The TiO2 (anatase) NPs enhanced exopolysaccharide (EPS) production by the test rhizobial cultures. The radical scavenging assay was performed to reveal the mode of action of the nano‐TiO2 particles. The study revealed higher reactive oxygen species (ROS) generation by the TiO2 (anatase) NPs as compared with TiO2 (anatase+rutile) NPs. Exposure to TiO2 NPs also altered the morphology of rhizobial cells. The findings suggest that TiO2 NPs could act as promoters of PGP traits of PGP bacteria when applied at appropriate lower doses.

Oxygen Level Controlled Polymorphic Transformation in Sol–Gel Processed Electrospun TiO2 Nanofibers

“…The lattice parameters for anatase are as follows: a = 3.7845 Å, c = 9.5143 Å, rutile: a = 4.5937 Å, c = 2.9587 Å and brookite: a = 5.4558 Å, b = 9.1819 Å, c = 5.1429 Å . Anatase phase exhibits highest photocatalytic activities among these phases, suppressing rutile, brookite, and artificial TiO 2 –B phase since the smaller crystallites size of anatase TiO 2 and low effective mass of its photogenerated charge carriers make the electron and hole recombination process slower. − Anatase nanocrystals under 10 nm are transparent, modulate light efficiently at low voltage, and are suitable for smart window applications. , In addition, anatase TiO 2 nanoparticles significantly contribute to agriculture sector by controlling bacterial condition on the roots of the plants and altering microorganisms of soils. − Thus, a convenient route to synthesize pure anatase phase of TiO 2 nanoparticles is critical for implementing them efficiently in different applications.…”