2nd Place: D3034: Unintended antibiotic target: The (honey bee) reproductive microbiome

Historically, honey bee queen lifespan was two to seven years, but now 50% of colonies replace queens within six months, doubling the chance of colony mortality. Colonies that are failing usually have queens with low sperm viability and drone (male) sperm counts are highly variable. Tetracycline is the most used antibiotic in beekeeping to treat common brood diseases and has been shown to decrease reproductive development, sperm viability, and overall success in rodent models. Tetracycline is classified as an endocrine disrupting chemical because of its mitochondrial inhibition in reproductive cells. Microbes have been discovered in reproductive tissues of many animals including insects and have been associated with offspring success. To date, no other studies have investigated if honey bees possess a reproductive microbiome or the impact of antibiotic exposure on bee reproduction. We hypothesized that queens and drones possess a reproductive microbiome and that exposure to antibiotics will perturb the native microbial community, which could lead to reduced fecundity. We have shown that antibiotics are highly toxic to drone sperm in-vitro and confirmed that ingested antibiotics accumulate in honey bee queen reproductive organs (via mass spec). In addition, we have shown that honey bee drones do have a reproductive microbiome by dissecting reproductive organs under sterile conditions, extracting DNA, and characterizing the microbial community. Lastly, after treating drones with less than field relative doses of tetracycline we have determined that oral antibiotic exposure perturbs the honey bee reproductive microbiome by reducing species diversity and absolute abundance.