Honeybee intestines retain low yeast titers, but no bacterial mutualists, at emergence

Authors: TAUBER, JAMES - Former ARS Employee; MCMAHON, DINO - Freie University; RYABOV, EUGENE - Volunteer; KUNAT, MAGDALENA - Maria Curie Sklodowska University; PTASZYNSKA, ANETA - Maria Curie Sklodowska University; Evans, Jay

Submitted to: Yeast
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2021
Publication Date: 1/17/2022
Citation: Tauber, J.P., Mcmahon, D., Ryabov, E., Kunat, M., Ptaszynska, A., Evans, J.D. 2022. Honeybee intestines retain low yeast titers, but no bacterial mutualists, at emergence. Yeast. 39(1-2):95-107. https://doi.org/10.1002/yea.3665.
DOI: https://doi.org/10.1002/yea.3665

Interpretive Summary: The honeybee intestine possesses characteristic bacteria that are obtained from nestmates after emerging from the comb’s cell. We investigated the presence of yeast throughout honeybee development, focusing on emerging worker bees. We found that, in contrast to bacteria and other microbes, the honeybee gut possesses a diverse set of yeasts at emergence, albeit at low density. We discuss possible active or passive roles played by these yeast species as worker bees commence in-hive nurse duties. The results have implications for bee development and health in response to stress.

Technical Abstract: Honeybee symbionts, predominantly bacteria, play important roles in honeybee health, nutrition and pathogen protection, thereby supporting colony health. On the other hand, yeasts are often considered indicators of poor bee health and honeybee microbiome studies generally exclude fungi and yeasts. We hypothesized that yeasts may be an important aspect of early honeybee biology. Especially if yeasts provide a mutual benefit to their hosts, honeybees could provide a refuge during metamorphosis to ensure the presence of yeasts at emergence. We surveyed for yeast and fungi during pupal development and metamorphosis in worker bees using fungal-specific qPCR, next-generation sequencing and standard microbiological culturing. Based on yeast presence in three distinct apiaries and multiple developmental stages, we conclude that yeasts survive through metamorphosis and in naïve worker bees, albeit at relatively low levels. In comparison, known bacterial mutualists, like Gilliamella and Snodgrassella, were generally not found in pre-eclosed adult bees. Whether yeasts are actively retained as an important part of the bee microbiota or are passively propagating in the colony remains unknown. Our demonstration of the constancy of yeasts throughout development provides a framework to further understand the honeybee microbiota.