Propolis envelope promotes beneficial bacteria in the honey bee (Apis mellifera) mouthpart microbiome

Authors: DALENBERG, HOLLIE - University Of Minnesota; MAES, PATRICK - University Of Arizona; Mott, Brendon; Anderson, Kirk; SPIVAK, MARLA - University Of Minnesota

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2020
Publication Date: 7/18/2020
Citation: Dalenberg, H., Maes, P., Mott, B.M., Anderson, K.E., Spivak, M. 2020. Propolis envelope promotes beneficial bacteria in the honey bee (Apis mellifera) mouthpart microbiome. Insects. 11(7):453. https://doi.org/10.3390/insects11070453.
DOI: https://doi.org/10.3390/insects11070453

Interpretive Summary: Honey bees collect and apply plant resins to the interior of their nest cavity, which is called a propolis envelope. Propolis has antimicrobial activity against honey bee pathogens, but the effect of propolis on the honey bee microbiome is unknown. Honey bees do not intentionally consume propolis but do manipulate propolis with their mouthparts. Because honey bee mouthparts are used for collecting and storing nectar and pollen, grooming and food sharing between adults, feeding larvae, and cleaning the colony, they are an important interface between the bees’ external and internal environments and serve as a transmission route for core gut bacteria and pathogens alike. We hypothesized that the antimicrobial activity of an experimentally applied propolis envelope would influence the bacterial diversity and abundance of the worker mouthpart microbiome. The results revealed that the mouthparts of worker bees in colonies with a propolis envelope had significantly lower bacterial diversity and significantly higher bacterial abundance compared to the mouthparts of bees in colonies without a propolis envelope. Based on taxonomic results, the propolis envelope appeared to reduce pathogenic or opportunistic microbes and promote the proliferation of putatively beneficial microbes on the honey bee mouthparts, thus reinforcing the native microbiome of the mouthpart niche.

Technical Abstract: Honey bees collect and apply plant resins to the interior of their nest cavity, which is called a propolis envelope. Propolis has antimicrobial activity against honey bee pathogens, but the effect of propolis on the honey bee microbiome is unknown. Honey bees do not intentionally consume propolis but do manipulate propolis with their mouthparts. Because honey bee mouthparts are used for collecting and storing nectar and pollen, grooming and trophallaxis between adults, feeding larvae, and cleaning the colony, they are an important interface between the bees’ external and internal environments and serve as a transmission route for core gut bacteria and pathogens alike. We hypothesized that the antimicrobial activity of an experimentally applied propolis envelope would influence the bacterial diversity and abundance of the worker mouthpart microbiome. The results revealed that the mouthparts of worker bees in colonies with a propolis envelope had significantly lower bacterial diversity and significantly higher bacterial abundance compared to the mouthparts of bees in colonies without a propolis envelope. Based on taxonomic results, the propolis envelope appeared to reduce pathogenic or opportunistic microbes and promote the proliferation of putatively beneficial microbes on the honey bee mouthparts, thus reinforcing the core microbiome of the mouthpart niche.