One out of every 3 mouthfuls of food consumed was pollinated by a bee. The honey bee is the most important agricultural pollinator in the US, adding $20 billion to the value of US crops annually. However, populations of honey bees are in decline due, in part, to pests and pathogens. In fact, the fungal pathogen Nosema is only second to the Varroa mite in the USDA list of stressors contributing to colony decline of honey bees (USDA Honey Bee Colonies survey, August, 2018). Without honey bees, large swathes of the agricultural economy would see declines in production. Combined with climate change, this loss in productivity will have a compounding effect on the ability to feed US citizens. Therefore, new technological innovations are needed to help mitigate the decline of honey bee colonies. This research will investigate a novel anti-fungal symbiont of honey bees, identify how it protects bees, and exactly what anti-fungal it produces. In addition to the benefits to bees, the discovery of novel anti-fungals may also have downstream benefits for human health in the fight against fungal pathogens, thus helping the bioeconomy. This project also supports the training of graduate students. Thus, this will support the education of the next generation of scientists who would ultimately work in the new bioeconomy.
The goal of this research is to identify how a honey bee symbiont protects brood, honey bee larvae, from fungal pathogens. The dramatic decline of the honey bee population is likely due to environmental stressors including limited floral resources (nutritional stress), pathogens (immune stress), and exposure to fungicides and pesticides (chemical stress). Data shown here discovered that a bacterial symbiont of honey bees protects against one of these significant stressors: fungal pathogens. Preliminary data suggest that the symbiont secretes anti-fungal metabolite(s) that protects bee brood from fouling; both in vitro assays and larval infection experiments support this conclusion. This project aims to characterize how this symbiont protects bees. How did this trait evolve across the phylogeny of bee-associated and flower-associated alphaproteobacteria? And what is the identity of the antifungal metabolite? Applicants will use a combination of microbial assays, in vitro bee rearing, genetics, genomics, and chemistry to answer these questions. This is the first time that the mechanism of symbiosis for an anti-fungal symbiont in bees has been explored, and will allow biologists to identify how specific members of the honey bee microbiome affect brood health. Additionally, because this symbiont is related to those found associated with wild bees and flowers, it presents an ideal model in which to explore the selection and maintenance in a symbiont, of a host-beneficial trait. Broader impacts include research training for graduate students, and creating a research experience program for undergraduate students at two institutions.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
