Cellophane bees of the genus Ptiloglossa culture multiple species and strains of Apilactobacillus bacteria (family Lactobacillaceae), which circulate among bees and flowers. These bacteria are highly active in the food provisions of the bees, where they play an important role as a source of nutrients for developing larvae.
An overview of the ecology of Ptiloglossa arizonensis in southeastern Arizona, showing major nectar (Agave) and pollen (Solanum) sources used to provision the larvae. Image credit: Hammer et al., doi: 10.3389/fmicb.2023.1114849.
“This discovery is quite remarkable,” said Dr. Tobin Hammer, a biologist at the University of California, Irvine.
“We know that lactobacilli are important for fermentation of food, but finding wild bees that use them essentially the same way was really surprising.”
“Most of the 20,000 species of bees get their nutrition from nectar and pollen, but for these cellophane bees, we suspect that lactobacilli are also really important.”
“They have effectively evolved from herbivores into omnivores.”
The authors also found that the food provisions of cellophane bees have much higher bacterial biomass compared to other bee species, matching the unusually fermentative smell that emanates from their brood cells.
These uniquely rich, lactobacilli-dominated microbreweries of cellophane bees could have important implications for the health of the bees, as well as for the ecology of the ecosystems in which they live.
“It was intriguing to find that cellophane bees use a strategy called ‘spontaneous fermentation,’ which is how certain fermented foods like sauerkraut are made,” Dr. Hammer said.
“Rather than passing on starter cultures from generation to generation, they use wild strains of lactobacilli that are ubiquitous in flowers.”
“It suggests that fermentation-based symbioses like this one can evolve without domestication.”
“What makes these bees special is that they’ve figured out how to create a favorable environment in which lactobacilli can grow really well.”
The study highlights the importance of studying the microbiomes of insects, which are often overlooked in favor of more familiar animals like birds and mammals, despite playing an enormous role in ecosystems the world over.
By understanding the complex interactions between microbes and their insect hosts, scientists can gain new insights into the biology of these important animals and the ecosystems that they inhabit.
“Ptiloglossa bees illustrate a path by which hosts can evolve quantitatively novel symbioses: not by acquiring or domesticating novel symbionts, but by altering the microenvironment to favor growth of already widespread and generalist microbes,” the researchers said.
The paper was published in the journal Frontiers in Microbiology.
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Tobin J. Hammer et al. 2023. Bee breweries: The unusually fermentative, lactobacilli-dominated brood cell microbiomes of cellophane bees. Front. Microbiol 14; doi: 10.3389/fmicb.2023.1114849
