Abstract
Lead (Pb) is a pervasive environmental pollutant that poses significant risks to both microbial communities and host physiology. However, the bidirectional interactions between Pb and insect gut microbiota, as well as the underlying mechanisms by which Pb disturbs microbiota homeostasis, remain poorly understood. Using Drosophila melanogaster as a model, this study investigates how Pb exposure affects the gut microbial ecosystem and how intestinal bacteria, in turn, influence Pb metabolism in the host. Among three tested concentrations, 100 mg/L Pb induced the most pronounced dysbiosis, characterized by reduced bacterial abundance and altered community composition, including an increased relative abundance of potential pathogens and a decline in beneficial taxa such as Lactobacillus. Pb exposure also suppressed antimicrobial peptide expression and activated stress-related JNK and JAK/STAT signaling pathways in the gut. Genetic suppression of these pathways restored bacterial abundance, suggesting their involvement in Pb-induced microbial imbalance. Conversely, Pb accumulation levels did not differ significantly between germ-free and conventional flies, although metallothionein expression was significantly upregulated in germ-free flies, indicating a compensatory detoxification response. These findings reveal a novel link between environmental Pb exposure and host-microbiota homeostasis mediated by specific immune signaling pathways. This work highlights important ecological implications for understanding the sublethal effects of heavy metal pollution on terrestrial insect health, with potential relevance for environmental risk assessment and ecosystem management.
