Bacteriostatic Effects of Apatite-Covered Ag/AgBr/TiO₂ Nanocomposite in the Dark: Anomaly in Bacterial Motility

In this paper, we report a unique property of inactivating Gram-positive/negative bacteria in the dark via apatite-covered Ag/AgBr/TiO₂ nanocomposites (AAAT). We demonstrate that the inactivation mechanism is bacteriostatic based on the cellular integrity and motility of bacteria, low toxicity and high durability of AAAT. From straight observations, the catalytic loading affects the bacterial replication and cell envelope as well as inducing an anomaly in bacterial motility (continuous rotation) for both types of bacteria. Both simulation and experimental analyses suggest that the anomaly could be due to posterior intracellular signals rather than purely mechanical effects (e.g., size enlargement and motility retardation). Provoked by chemomechanical stimuli, these signals increase the frequency of flagellar tumbling and eventually entangle the bacteria.