Bees recognize each other through their microbiome
Members of an “Apis mellifera” colony share the same olfactory signature, emitted by their cuticular hydrocarbons and linked to a specific intestinal bacterial flora.
Abstract
A recent US study (Cassondra L. Vernier et al., 2020) has shown that in the honey bee, the genetically related members of a colony innately develop colony-specific profiles of cuticular hydrocarbons that serve as recognition cues for the pheromonal identity of that population. However, despite the high degree of relatedness within a colony, the innate development of individual, colony-specific chemical signatures is largely determined by the environment within the hive, rather than depending solely on the genetic variants shared by the individuals of that colony. This raises the question of how a non-genetic factor can give rise to the innate development of a quantitative trait shared by all members of the same colony. The researchers provide an answer to this puzzle by showing that, in honey bees, colony membership recognition cues are defined, at least in part, by shared characteristics of the gut microbiome among members of the same colony. These findings illustrate the importance of host–microbiome interactions as a source of variation in animal behavioural traits.
The comings and goings of foragers leaving and returning to their colony are closely monitored by the guard bee (Image: Susanne Jutzeler)
The gut microbiome as a determinant of social group membership in honey bees
Honey bees recognize nestmates through colony-specific blends of cuticular hydrocarbons (CHCs). Although colony members are genetically related, these recognition cues are largely shaped by environmental factors. This study tests the hypothesis that the gut microbiome is a key environmental driver of colony-specific chemical signatures.
Comparative analyses reveal that foragers from different colonies possess distinct gut microbial communities and clearly different CHC profiles. Overall bacterial diversity is similar across colonies, but the relative abundance of specific core microbes differs. Cross-fostering experiments show that adult gut microbiomes are primarily determined by the post-emergence social environment rather than by genetic origin.
Causal evidence is provided through experimental manipulations. Antibiotic treatments, inoculation with live versus heat-killed microbiomes, and targeted colonization with specific bacteria all alter CHC profiles. The symbiotic bacterium Gilliamella apicola plays a central role: bees carrying this microbe preferentially accept other bees with the same microbial profile, regardless of genetic relatedness. Opportunistic bacteria do not produce this effect.
Strikingly, even strain-level genetic variation within a single bacterial species is sufficient to generate distinct CHC profiles and affect recognition behavior. Different strains of G. apicola induce measurable differences in chemical signatures and nestmate discrimination.
The authors interpret these findings within the holobiont framework, proposing that social identity in honey bee colonies emerges from interactions between host and microbial genomes. Gut microbes likely influence CHC synthesis indirectly, for example by providing metabolic precursors or modulating host biosynthetic pathways.
In conclusion, the gut microbiome is a fundamental contributor to social group membership in honey bees, highlighting the importance of host–microbe interactions in shaping complex social behaviors.
Download the article (English) as a PDF
See also:
- Beneficial microbes for bee health
- A very social immunity
- Pheromones as drivers of behavioural plasticity
- Epigenetics leads genetics
- The bee genome
