Induction of Oxidative Hormesis by TiO2 Nanoparticles Enhances Antibacterial Activity of Lactobacillus acidophilus

Abstract

Objective: The aim of this study was to investigate the potential induction of oxidative hormesis in probiotic Lactobacillus acidophilus by metal oxide nanoparticles. Special attention was given to the effect of different types of nanoparticles to trigger oxidative hormesis, influnce on bacteriocin synthesis and the antibacterial activity of the strain against antibiotic-resistant pathogens. Methods: This study employed sol-gel and precipitation methods to synthesize various metal oxide nanoparticles, which were characterized for their physicochemical properties and tested for their effects on Lactobacillus acidophilus growth. The interaction between TiO₂ nanoparticles and bacterial cells was analyzed using EDX and hydrogen peroxide assays, while gene expression related to oxidative stress and bacteriocin production was quantified by qRT-PCR, demonstrating enhanced antibacterial activity via oxidative hormesis. Results and Discussion: Research on the toxic effects of metal oxide nanoparticles (NPs) has primarily focused on their negative impact on bacterial growth and metabolism, which are well-documented. This study describes a positive influence of NPs despite predominant data about toxicity and confirms that TiO₂ NPs stimulate an increase of bacteriocin synthesis through oxidative hormesis induction. The described effect was reached by TiO₂ NPs at 15 μg/mL and resulted in a twofold increase in bacterial cell count. Oxidative hormesis induction was confirmed by enhanced gene expression associated with repair mechanisms and reactive oxygen species neutralization systems. Linkage of oxidative hormesis and antibacterial properties was shown by 8 bacteriocin genes expression increasing up to 6 times. This data determined the statistically significant increase in the inhibition zones of E. coli and S. aureus by 1.5 and 2.6 times, respectively. Conclusions: The obtained results provide a new approach to manipulating the antibacterial metabolism of Lactobacillus sp. for applications in both biotechnology and the development of biohybrid systems for personalized antibacterial therapy.