Environmental transmission of bacteria and its implications for wild bees

The microbial communities within insect microbiomes are profoundly shaped by lifestyle, habitat, and the physicochemical environments within their digestive tracts. Particularly in bees, these communities are further influenced by their social or solitary nature. Social bees tend to exhibit a conserved microbiota facilitated by behaviors such as trophallaxis and nest grooming, which promote microbial transference between generations. In contrast, solitary bees, such as Osmia lignaria, often display greater microbial diversity, potentially due to environmental transmission mechanisms. We researched the environmental transmission of Apilactobacillus micheneri, an acidophilic, fructophilic bacterium prevalent in fructose-rich environments and associated with the pollen provisions of ground-nesting bees. We experimentally tested whether Apilactobacillus micheneri can be transmitted environmentally from bees inoculated with the bacterium to those not previously exposed, using Osmia lignaria and Phacelia tanacetifolia as our model system. We found that environmental transmission occurs from flowers to bees and vice versa. We discuss the potential influence that environmental transmission in adult bees might have on the host’s next generation.