Toxicity Assessment of Titanium Dioxide Nanoparticles in E. coli Mutant with Truncated Lipopolysaccharide (LPS)

Abstract

As the production and use of titanium dioxide nanoparticles (TiO₂NPs) have increased, so has concern over their environmental impact. Bacteria play an important role in ecological processes and may be harmed by these nanoparticles' toxicity. The specific mechanisms of TiO₂NPs toxicity towards bacteria, as well as the primary role of bacterial cell surface composition, are so far not fully recognized. The impact of TiO₂NPs exposure on both wild strain, E. coli K 12 W3110, and LPS biosynthesis pathway galU gene mutant was assessed in the present study to gain insight into the underlying mechanisms contributing to TiO₂NPs toxicity. We demonstrate that a truncated LPS causes increased sensitivity to TiO₂NPs. During the experiment, TiO₂NPs formed aggregates with bacteria, and the electrophoretic mobility test revealed a higher interaction between nanoparticles and bacteria due to the positive and negative charge on their surfaces. The high sensitivity of the galU mutant to TiO₂NPs may be attributed to the shorter LPS and also possibly with outer membrane efflux proteins like TolC and porins/OmpF, which provide stability to the outer membrane while also acting as permeability barriers to hazardous substances like chemicals, detergents, antibiotics and nanoparticles.

HIGHLIGHTS

• The present study highlights the role of the morphological features of bacteria involved in TiO₂NPs toxicity at the molecular level
• LPS in the bacteria act as an efficient barrier function as truncated LPS makes the bacteria more sensitive to TiO₂NPs
• The changed expression of TolC efflux proteins and OmpF/C porin proteins due to galU mutation can possibly lead to disturbed cell signaling and instability of the outer membrane

GRAPHICAL ABSTRACT