#The hidden power within - studying the honey bee microbiome ##Vienna & Sasha

The fact that we, no matter where we are, are surrounded by for our eyes invisible tiny organisms - microorganisms - is fascinating. Microbial communities are small worlds for themselve, full of interactions. The great influence that microorganisms have on their environment is something we just started to understand.

The realization that we are not only surrounded by, but that in fact all multicellular organisms are closely associated with diverse microbial communities with profound effects on host life history traits – revolutionized our understanding of animal biology. There is a current need for a mechanistic understanding of interactions between members of microbial communities and their hosts, knowledge that will facilitate discovery of exciting new facts in animal biology. The knowledge to functionally understand and manipulate microbiomes could be usefully applied to diverse research areas such as health or agriculture. Yet, the complexity of microbiomes with interactions between members, and their consequences on hosts make most host-microbiota systems difficult to study. The experimentally tractable system of the honey bee offers an ideal opportunity to fundamentally explore functions and interactions of symbionts on host fitness, as the associated microbial communities are small, specialized, and individually cultivable.

Our goal is to get fundamental insights into host-microbiome relationships using the honey bee and its symbionts as model system. To do that we are using a combination of molecular methods and controlled experiments.

We are currently trying to tackle several project questions but mainly the two below:

1) Meta-transcriptomics, exploring genotype-derived microbiome differences over time

The microbiome can provide its host with flexibility beyond that encoded in host genomes, as rapid changes in microbial community composition or individual microbial genomes can directly affect important host life history traits. Therefore, the microbiome may enable rapid acclimation to new environments and resistance to environmental disturbances.

We can take advantage of a historical, unique data set consisting of many hundreds of honey bees sampled for more than a decade in the U.S. and Mexico, to generate a detailed picture of the internal microbiome, as well as of associated virus and host transcriptome responses by total RNA sequencing. During this time, a hybridization event from introduced African with wild US-European bee lines occurred. This invasion of the western hemisphere by the African honey bee genotype in less than 50 years and the subsequent spread of the Africanized hybrids is one of the most successful and rapid biological invasions known. Diverse genetic bee backgrounds in the same natural environment, will allow me to examine how host genetics affect microbiomes in the field.


2) Functional experimental tests on microbiota-mediated effects

Several studies could already demonstrate that the microbiome plays a crucial role in honey bee health and that a disturbed microbiota (e.g. due to antibiotic treatment) will result in sick bees. This is particularly important as honey bee health has been a major concern, following colony losses worldwide in the last decade. Still, we just started to realize the importance of the microbiome in this story and there are still many open questions that need to be answered. Raising honey bees under sterile conditions in the lab give us the option to do controlled experiments to disentangle the effects and interactions between microbial members, the host and stress factors. Research can be like a puzzle and if enough puzzle pieces have been found, they need to be put together to get a picture. If this can be managed in the promising honey bee system, it could lead to new ways of tackling current problems. For example by avoiding specific antibiotic treatments which are thought to protect the bees but are disturbing their microbiome, or by providing bee probiotics.

In terms anybody is interested in more information about the awesome honey bee - microbiome system, I would recommend some beautiful reviews on it, which give a very nice overview about the topic as well as current knowledge and development in this research area:

Evans, J.D., and Schwarz, R.S. (2011). Bees brought to their knees: microbes affecting honey bee health. Trends Microbiol. 19, 614–620. Kwong, W.K., and Moran, N.A. (2015). Evolution of host specialization in gut microbes: the bee gut as a model. Gut Microbes 6, 214–220. Moran, N.A. (2015). Genomics of the honey bee microbiome. Curr. Opin. Insect Sci. 10, 22–28. Schwarz, R.S., Huang, Q., and Evans, J.D. (2015). Hologenome theory and the honey bee pathosphere. Curr. Opin. Insect Sci. 10, 1–7. Kwong, W.K. and Moran, N.A., 2016. Gut microbial communities of social bees. Nature Reviews Microbiology, 14(6), p.374. Raymann, K. and Moran, N.A., 2018. The role of the gut microbiome in health and disease of adult honey bee workers. Current Opinion in Insect Science.