Effects of TiO₂ nanoparticles on intestinal microbial composition of silkworm, Bombyx mori

The widespread use of nanomaterials has raised concerns about the potential impact of nanoparticles on human health and the natural environment. Although high doses of TiO₂ nanoparticles (NPs) are toxic to animals, low doses of TiO₂ NPs have been shown to benefit their growth and immune functions. Intestinal microorganisms are critical in maintaining the normal life activities and ensuring the health of their host. The intestinal microorganisms of lepidopteran insects can promote growth and development, foster insecticide resistance, and improve resilience against diseases. However, to date, there is no report on the effects of TiO₂ NPs on the intestinal microbiota of lepidopteran insects. In this work, we examined the effects of a low dose of TiO₂ NPs (5 mg/L) on the intestinal microbiota of silkworm (Bombyx mori). The results showed that the exposure to TiO₂ NPs did not alter the dominant species of intestinal microbiota significantly, but changed the abundance of individual species of intestinal microorganisms. Specifically, exposure to TiO₂ NPs increased the uniformity of intestinal microorganisms. The abundance of Lachnospiraceae_NK4A136_group, involved in the metabolism of nutrients, as well as the abundance of Pseudomonas and Sphingomonas, both involved in detoxification and disease resistance, was increased. Meanwhile, among the non-dominant species, the conditional pathogenic bacteria Serratia exhibited decreased abundance. In addition, exposure to TiO₂ NPs also increased the abundance of norank_f_Bacteroidales_S24-7_group, which could help relieve inflammation and regulate immune functions. The current study is the first to report the effects of TiO₂ NPs on the intestinal microbiota of lepidopteran insects. The results demonstrated that TiO₂ NPs could alter the composition of the intestinal microbiota of B. mori, and thus promote its growth and development, regulate its immune functions, and enhance its resistance to insecticide.