Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Biology

Supervisor

Thompson, Graham J.

Abstract

The Western honey bee, Apis mellifera, is vulnerable to disease, especially disease afflicting the brood. To counter this, bees exhibit hygienic behaviour: nurse bees detect olfactory cues indicative of disease and remove affected pupae. Selecting for this trait is challenging for beekeepers, who may instead resort to quick-fix antibiotics. In this thesis, I explore the potential of beneficial bacteria (“probiotics”) to promote hygienic behaviour. I fed bees two species of lactic acid-producing bacteria that may help synthesize olfactory-associated neurotransmitters, then tested for changes in hygiene and microbial diversity. I detected small increases in hygiene and small changes to microbiota composition in the short term, but these treatment effects were generally small and variable. This research nonetheless provides a foundation for a field study with more power to detect small but potentially significant differences through the bee gut-brain axis, which could ultimately serve the beekeeping community by providing recommendations for best practices.

Summary for Lay Audience

Honey bees live in large colonies of closely related individuals, making them vulnerable to the spread of disease. Many of these diseases target the brood, which are tightly packed in cells and can readily spread infection. The brood is cared for by 15-20 day-old worker bees (‘nurses’). To prevent the spread of infection, nurses detect scents emitted from dead or diseased brood and then remove the brood from the colony. This behaviour, known as hygiene, is invaluable to beekeepers, but it can be difficult to breed for due to its complex genetic basis. Consequently, beekeepers often use antibiotics, despite side effects like antibiotic resistance and disruption to the gut microbiota. In my project, I draw from the growing field of probiotics to determine if certain bacteria can promote hygiene within colonies. I supplemented hives with two species of bacteria that may help produce the brain’s chemical messengers (neurotransmitters). Specifically, neurotransmitters potentially relevant to olfactory (scent) disease detection. Then, I tested for effects on the expression of hygienic behaviour. I also sequenced the guts of nurse bees to determine which bacterial species were present before and after probiotic treatment. Despite a lack of statistically significant treatment effects, I did see small changes in the expression of hygienic behaviour, as well as some changes in the composition of the gut bacterial community, suggestive of a possible acute treatment effect. Lastly, I interpret my behavioural and gut microbial community results in the context of how they might affect beekeeping practices.

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