Antibiotic exposure can perturb the gut microbiota of honey bees, but its associations with host physiological responses remain incompletely understood. Here, we investigated the effects of tetracycline exposure on survival, locomotor activity, gut bacterial communities, and immune- and antioxidant-related gene expression in Apis mellifera workers maintained under controlled laboratory cage conditions. Tetracycline exposure at 100, 300, and 450 μg/mL reduced worker survival in a concentration-dependent manner, while 100 μg/mL increased daytime locomotor activity without affecting sucrose consumption. Tetracycline also altered gut bacterial community structure, with marked reductions in several core taxa, particularly Snodgrassella and Bartonella, whereas Commensalibacter, Lactobacillus Firm4 and Firm5 increased, especially at the highest concentration. Changes in immune- and antioxidant-related gene expression were more pronounced in the gut than in the head. Moreover, Snodgrassella abundance was positively correlated with Relish expression in the head and with Apidaecin and CAT expression in the gut. These findings demonstrate that tetracycline exposure reduces honey bee survival and is associated with coordinated alterations in gut bacterial communities and host physiological responses.

Pollen is one of the main food sources for honeybees. The honeybee gut microbiota plays a crucial role in maintaining digestive function and host health during long-term coevolution. While the consumption and utilization of pollen have been extensively studied, there is limited information about the effects of pollen on the gut microbiota of Apis cerana. In this study, we used 16S rRNA amplicon sequencing to evaluate the effects of four natural pollens (oilseed rape pollen, camellia pollen, lotus pollen and buckwheat pollen) and two pollen substitutes (Diet 1 and Diet 2) on the hindgut microbiota of newly emerged A. cerana worker bees, following feeding periods of 5, 10 and 15 days. The results showed that Firmicutes and Proteobacteria are dominant in the gut microbiota of A. cerana. A. cerana workers fed with pollen diets had a higher diversity of gut microbiota than those fed with pollen substitutes. There have been significant differences in the gut microbiota structure and relative abundance of the core microbial community among A. cerana workers supplied with different diets. Our results confirm that gut bacterial communities of A. cerana can be influenced by pollen diets and may play an important role in host adaptation.