Priority Effects in the honeybee gut

Through this study we aim to understand how bacterial strains in the gut microbiome interact with each other. Gut microbial communities often differ at the strain level even among closely related individuals, but the ecological mechanisms driving this variation remain poorly understood. One potential driver is priority effects, differences in the timing and order of microbial colonization, which can lead to the assembly of distinct communities, even under similar environmental conditions. Priority effects may specifically play an important role in shaping microbial communities at the strain level, given that strains of the same species typically occupy similar ecological niches. To test this, we examined gut microbiota assembly in honeybees, in which age-matched nestmates are known to host similar microbial communities at the species level but vary in strain composition. We sequentially colonized microbiota-depleted honeybees with two distinct microbial communities, each composed of the same twelve species but different strains. We found that firstcomer strains consistently dominated the resulting communities, though the strength of these priority effects varied among closely related strains and species. Dropping out individual strains from the firstcomer community only partially improved the colonization success of latecomer conspecifics, suggesting that priority effects also act across species boundaries. Our results underscore the importance of priority effects for gut microbial community assembly at the strain level and in shaping the specialized gut microbiota of bees.

Context:

• Understanding the factors influencing and maintaining strain-level community composition in microbiomes is crucial for predicting and manipulating microbial communities.
• Microbe-microbe interactions in the context of a microbial community at the strain-level are still understudied.
• Honeybees are a great model to study this in vivo due to their simple gut microbiome and the experimental tractability of the host and microbiota.

Challenge: * Investigating priority effects in a community of Lactobacillus and Bifidobacterium strains in the honeybee gut. * Developing a high-throughput compatible PacBio metagenomic approach to quantitatively detect strains in the gut.

Expectations and Results:

• We expect that the priority effects will be seen at the strain-level and that species will coexist by niche partitioning as has been shown among in honeybee Lactobacillus species by a collegue.
• We have developed a high-throughput compatible PacBio metagenomic approach to quantitatively detect strains in the gut.
• A pilot experiment points to clear signs of co-existance of species but priority effects between strains of the same species.
• I carried out more replicates and combinations of strains and am currently analyzing the data to confirm the observations from the pilot experiment.