Abstract
Gut microbial community plays an important role in the regulation of insect health. Antibiotic treatment is powerful to fight bacterial infections, while it also causes collateral damage to gut microbiome, which may have long-lasting consequences for host health. However, current studies on honey bees mainly focus on the impact of direct exposure to antibiotics on individual bees, and little is known about the impact of social transmission of antibiotic-induced gut community disorder in honey bee colonies. In order to provide insight into the potential pass-on effect of antibiotic-induced dysbiosis, we colonized newly emerged germ-free workers with either normal or tetracycline-treated gut community and analyzed the gut bacteria composition. We also treated workers with low dosage of tetracycline to evaluate its impact on honey bee gut microbiota. Our results showed that the tetracycline-treated gut community caused disruption of gut community in their receivers, while the direct exposure to the low dosage of tetracycline had no significant effect. In addition, no significant difference was observed on the mortality rate of A. mellifera workers with different treatments. These results suggest that though the residue of antibiotic treatment may not have direct effect on honey bee gut community, the gut microbiota dysbiosis caused by high dosage of antibiotic treatment has a cascade effect on the gut community of the nestmates in honeybee colonies.
Highlights
Honey bee (Apis spp.) is one of the most important insect pollinators, contributing an estimated 153 billion euros to the world’s agriculture in 2005 (Gallai et al, 2009)
Antibiotics are used in beekeeping practice to treat or prevent bacterial infections (Piva et al, 2020), such as American foulbrood disease and European foulbrood disease, which are caused by Paenibacillus larvae and Melissococcus pluton (Arbia and Babbay, 2011), respectively
The absolute abundance of gut bacteria was significantly reduced in antibiotic treated (AT) workers compared to conventional gut community (CV) workers in all the four replicates (Figure 1A, student’s t-test: for E1: t = 3.14 df = 8, p = 0.0138; for E2: t = 2.151, df = 8, p = 0.0079; for E3: t = 2.894, df = 8, p = 0.0201; for E4: t = 3.158, df = 8, p = 0.0134). 16s rDNA amplicon sequencing demonstrated that Lactobacillus, Frischella, Commensalibacter, Bartonella, Snodgrassella and Gilliamella are the core bacterial species dominating in CV workers and Antibiotic treated (AT) workers (Figure 1B)
Summary
Honey bee (Apis spp.) is one of the most important insect pollinators, contributing an estimated 153 billion euros to the world’s agriculture in 2005 (Gallai et al, 2009). Parasites, nutritional and environmental factors, gut microbiota has been recently proved to be another important factor associated with honey bee health (Clemente et al, 2012; Brodschneider et al, 2018). Li et al (2017) revealed that penicillin-streptomycin treatment weakened bacterial activity in honeybees, which may negatively affect expression levels of genes encoding antimicrobial peptides and increase the honey bee’s vulnerability to Nosema infection. These studies provided important insights into how antibiotic treatment affects honey bee gut community and health, while they mainly focused on the direct impacts on the individuals that received the antibiotic treatment. It is vital to investigate the possible passon effect of the impact of antibiotics on honey bee gut community, especially on the development of gut community of their nestmates
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