Boosting Bee Health With Probiotics and Vaccines
This article was originally published in February 2023 and has since been updated for inclusion in the Spring 2024 issue of Microcosm.
The driving forces of colony collapses are both complex and unclear, but they are crucial to understand if we want to protect honeybees and the ecosystem and economic services they provide. Thus, bee health is an important focus of both scientific research and conservation efforts around the world. Researchers are considering as they study how these kinds of perturbations affect the survival, behavior and gut microbiota of honeybees. Some of these dangers have microbial origins, and some even have microbial solutions.
Honeybee Gut Microbiome Offers Clues
One particularly microbe-dense habitat is the gut, which is just as important for insects, such as honeybees, as it is for mammals like humans. Though the, it provides many benefits for their health. These include improved growth, digestion and protection from opportunistic pathogens.
What’s more, the gut microbiota may play a role in what is known as the gut-brain axis, the 2-way communication between gastrointestinal tract and the central nervous system. Scientists have shown that the gut microbiota affects the , as it appears to be important for mediating social interactions and parsing sensory information from their environment. Bees use such social cues to transmit information amongst themselves, helping them to navigate the world around them and underscoring the importance of the gut microbiota for a functional hive.
In honeybees, as in other animals, a healthy gut microbiota is crucial for a healthy host. However, much like ours, the honeybee gut microbiota is also vulnerable to disturbances that induce a disrupted state known as dysbiosis. Threats come from many sides: antibiotics, habitat loss, , and even the wide-reaching impacts of climate change. Dysbiosis in the gut can leave honeybees more vulnerable to pathogens and negatively impact their health.
Pro-bee-otics
Given the importance of the gut microbiota, some bee health efforts start with microbiota-focused treatments. In an approach similar to interventions for human gut disorders, some researchers are looking to to protect honeybees from gut dysbiosis and its negative effects. Although robust evidence for the efficacy of probiotics in honeybees is still mostly lacking, at remaining in the gut after the probiotic treatment has stopped than commercial probiotic mixes that are not necessarily bee-derived.
Engineering Probiotics to Combat Deformed Wing Virus
However, researchers are now beginning to understand how protection against these pathogens can come from within. In one study, researchers genetically engineered Snodgrassella alvi, 1 of the 5 core honeybee gut microbes, to and mount the . In this response, the immune system recognizes exogenous double stranded RNA (dsRNA) inside cells and degrades any matching dsRNA by chopping it up. This response can be harnessed to target pathogen-specific RNA, although directly injecting targeted dsRNA has had limited success in honeybees. However, engineering S. alvi to produce it inside the host was highly effective at protecting bees against both Varroa and DWV.
Added Protection Against Varroa ​M¾±³Ù±ð²õ
For DWV, S. alvi produced dsRNA matching sections of the viral genome, priming the bees to chop up matching RNA belonging to the virus, while the mechanism for fighting Varroa was slightly more complex. When Varroa mites parasitize bees, they eat dsRNA-containing fat bodies on the bee thorax and abdomen. When the mites ingested dsRNA matching 14 of their own essential genes, produced by S. alvi in the gut, the bees were protected from infection as the dsRNA triggers the mites’ RNA interference response, leading them to chop up their own RNA. Although it is a , whether this kind of technology can be scaled up to protect entire hives from different kinds of diseases is still an open question.
The First Honeybee Vaccine Generates Buzz
In addition to these new insights in the field of probiotics, major strides in vaccine development are changing the way we look at American foulbrood, a widespread bacterial disease that causes colony collapses. In Jan. 2023, the U.S. Department of Agriculture (USDA) authorized the first oral vaccine to . The vaccine technology rests on feeding inactivated Paenibacillus larvae (the causative agent of the disease) to the queen bee via the royal jelly, her special food source. Once the queen bee ingests the vaccine, her body produces antibodies that propagate into her eggs. This also renders her progeny, P. larvae’s target, immune. This vaccine technology paves the way for protection of honeybees, as well as other insects, against other microbial threats.
Bee-yond the Honeybee
Although significant progress has been made, some argue that the , as they are by no means the only pollinators on the block. For example, wild bees are an incredibly diverse group comprising around 20,000 species.
While wild bees don’t produce honey, they are extremely important members of ecosystems in their own right. , limiting the microbially minded steps we can take to protect them.
Saving the bees—both honey- and wild—is an ongoing global effort. Understanding bees from the inside out can help us to protect them from some of the threats they face, though we cannot lose sight of larger issues, like habitat loss and climate change, to which the above interventions are little more than a band-aid.
Interested in learning more about the factors that are threatening bee colony survival? Check out this next article, which explains microscopic and macroscopic bee stressors, as well as what can be done to help address the problem.
