Gut Microbiomes & Hygienic Bee Behaviour.

Introduction.

April got off to a good start here in the Scottish Highlands with sunny days and a high of 18°C on one of them. It’s set to last another week at least which will be good for an oil seed rape nectar flow less than half a mile away. The flowers are just starting to open.

I felt inspired after watching Steve Riley’s presentation on The Honey Bee Solution to Varroa this week, https://www.youtube.com/watch?v=dcJO19QHAKE&t=8s . Steve is a very good speaker and skilled at answering the questions at the end which is often the most challenging part of a presentation. I feel even more motivated today after a Zoom chat with Theresa the author of Dead Bees Don’t Make Honey https://www.beelistener.co.uk/?s=theresa+martin . I’m ready for the season with supers poised.

I’ve assessed a couple of wee colonies in nucleus boxes but left the rest alone to expand a bit more. They all came through the winter with two of the seven very strong and ready for supers. No flying drones to be seen yet. Sticking with six colonies max is hard for me, but I need to keep them as well spaced as I can and be disciplined about it. I get fond of each colony and want to hang on to them all. I’m moving one nuc closer to the observation hive shed to install there soon. I’ve got a new wee bee apprentice coming soon and his parents will not want him getting stung yet so the observation hive is the place to start lessons. Another nuc will go to new beekeeper Louise once we have marked the queen together next week.

Gut Microbiome.

We talked about gut microbiomes a few months ago in relation to research findings asserting that non-native gut bacteria were not utilised by honey bees so that probiotics currently on the market are probably ineffective. It doesn’t mean that researchers will not discover evidence to promote and enable the manufacturing of useful probiotics to supplement bee nutrition in the future.

The role of good gut bacteria in honey bees is much more complex than we might think. Not only does the microbiome influence the immune system, growth and development; it also affects neurophysiological function and behaviour. 

Hygienic Behaviour & Good Guts.

Tola et al.¹ recently discovered an association between gut bacteria and hygienic behaviour. Social immunity of honey bees consists of several behaviours that may be described as hygienic behaviour, and the one assessed in this study was based on the detection of unhealthy brood odours (UBO) and the cell uncapping and removal of diseased brood. Although this is effective at removing bees and enhancing disease resistance, there is a risk of the nurse bees being exposed to pathogens during removal and cannibalisation of pupae.

The scientists collected bees from two colonies found to be hygienic according to the score allocated based on the number of pupae removed from cells, in a given time, after being sprayed with the synthetic UBO developed by Dr Kaira Wagoner (https://www.youtube.com/watch?v=aBnwK2L-Ozk )

Above 60% removal is good but these bees scored 71 and 91% for this hygienic behaviour. From these two colonies two groups of bees were selected. One group was chosen from nurse bees seen feeding larvae (non-hygienic behaviour), and the second from nurse bees observed uncapping and removing pupae (hygienic behaviour). Gut sampling of all the bees was carried out using sophisticated DNA sequence testing. What they found was that the hygienic behaviour bee groups had higher levels of some members of core bacterial communities than the non-hygienic behaviour bee groups did. You can see for example that levels of Lactobacillus apis and Frischella perrara and others differ between the two groups on the left and the two on the right.

When bees perform hygienic behaviour, they touch infected brood and come in contact with pathogens, disease and parasites. This activates an immune response leading to higher levels of antimicrobial peptides which are a key part of the honey bee immune system. They are energetically expensive for the bee to manufacture but important in protecting against high levels of deformed wing virus that cannibal bees may ingest.

Because research rarely gives the full picture, and the scientists are not certain if increased hygienic behaviour is caused by a particular bacterial community, or if the removal of diseased brood alters the gut microbiome, they advocate further research that will enable the development of feeding supplements which will improve bee health and, in particular, queen rearing operations, and preparing bees for stressful truck journeys to pollination contracts.

Another study, Vernier et al.², found that gut microbes have a role to play in the differences in foraging intensity between bees in a colony. Their study revealed that age-dependent differences in behaviour were associated with differences in the gut microbiomes between nurse bees and foragers. Another fascinating revelation comes from research by Wang et al.³ and demonstrates how gut microbes in the bee foregut help process nectar into honey. Bacteria boost levels of the enzyme amylase which is essential for conversion of carbohydrates to sugars. The scientists calculated amylase levels in both oil seed rape flower nectar and honey bee guts. Then they added bacilli to the nectar sample and what they discovered was that the nectar then had a 2.5 times higher amylase level than the bee gut sample. They concluded that more research is needed to find out the exactly what caused amylase levels to rise, because their work didn’t actually prove that bacteria produce amylase despite the strong evidence.

Where does all this leave us? Once again, this appeals to beekeepers to keep open minds and keep searching for more ways to improve bee health and reduce stress in colonies. Are our bees exposed to fungicides that will interfere with good gut bacteria? Do we know our local farmers and what they are putting on crops? Are there new probiotics on the market that more closely resemble natural bee microbiomes in terms of bacteria? We need to remain positive and keep on improving our own management. For starters, I’m searching the varroa boards for chewed out pupae with my super duper magnifying glass, and learning from Steve Riley’s work this year.

References:

¹Tola, Y.H., Wagoner, K., Strand, M.K., Rueppell, O. and Tarpy, D.R., 2025. The gut microbiome differs between hygiene-performing and non-hygiene-performing worker honey bees. Insectes Sociaux, pp.1-8.

²Vernier CL, Nguyen LA, Gernat T, Ahmed AC, Chen Z, Robinson GE. Gut microbiota contribute to variations in honey bee foraging intensity. ISME J. 2024 Jan 8;18(1):wrae030. doi: 10.1093/ismejo/wrae030. PMID: 38412118; PMCID: PMC11008687.  https://doi.org/10.1093/ismejo/wrae030

³Wang, M., Zhao, W.Z., Xu, H., Wang, Z.W. and He, S.Y., 2015. Bacillus in the guts of honey bees (Apis mellifera; Hymenoptera: Apidae) mediate changes in amylase values. European Journal of Entomology, 112(4).