Flowers serve as a hub of transmission of putatively probiotic bacteria to wild bees

Background/Question/Methods

While social transmission drives the specificity of the honey bee and bumble bee microbiota, other social Hymenoptera associate with environmentally acquired bacteria.  For example, Lactobacillus kunkeei consistently associates with multiple species of wild bees and flowers, suggesting that L. kunkeei is environmentally acquired and not host-specific.  These microbes, however, appear to share many characteristics with host-specific, socially-transmitted microbes that form the core honey bee and bumble bee gut microbiota.  Here I show that flowers are a source of putatively probiotic bacteria such as L. kunkeei.

Results/Conclusions

I recently sequenced several genomes of these flower- and bee-associated bacteria and found putatively host-benefitting genes.  I  also conducted a survey of flowers and megachilid bees that shows that while the bacterial communities from bees and flowers differ, bacteria like L. kunkeei and Arsenophonus are found in bees, flowers that have been visited by bees, and flowers from which bees were excluded.  Together these data suggest that a “spandrel” view of symbiosis, at least in wild bees, may be more apt than the coevolved or hologenome view.