Engineered bacteria can protect honeybees

The genetically modified strain would live in the gut of honeybees and produce medicines to protect against diseases

In recent years, beekeepers have suffered huge losses of their honeybees because of colony collapse. Long, harsh winters, starvation, poor or failing queens, habitat loss, weak colonies, and parasites and viruses have combined to killed millions of bees, in some cases causing catastrophic losses of hives.

According to the Canadian Association of Professional Apiculturists’ (CAPA) report, the national wintering loss of honeybees in 2018-2019 was 25.7 percent with provincial losses ranging from 19.8 percent (Nova Scotia) to 54.1 percent (Prince Edward Island). That wintering loss was considered to be the middle range of losses since 2007.

However, in the United States, beekeepers lost nearly 40 percent of their colonies last winter, the highest rate reported since the survey began 13 years ago.

Now, scientists at The University of Texas at Austin have developed a new strategy to protect honeybees with the application of a genetically modified strain of bacteria.

Bees have an ecosystem of gut bacteria called a microbiome and an antiviral defence mechanism known as RNA interference (or RNAi). It helps the body fight off RNA viruses. According to the university’s news release, the GM strain of bacteria will live in the gut of honeybees acting as tiny biological “factories” by pumping out medicines to protect the bees against two major threats: varroa mites and deformed wing virus.

The mites and the virus are associated together. As the mite consumes the fat body tissue of the honeybee, it transmits the deformed wing virus, further weakening the bees and making them vulnerable to a range of pathogens.

“We thought of this based on a lot of background work on the bee gut bacteria and knowing about the RNA interference pathway,” said Nancy Moran, professor with the Department of Integrative Biology, College of Natural Sciences. “Others have worked on this pathway in honeybees so we put together different kinds of information and had the idea of using the bacteria for protection.”

She said that the genetically engineered bacteria encode small stretches of DNA that in turn encode double stranded RNA made to match the RNA sequences of the virus or the mite.

“This is only a tiny part of the genome of the bee gut bacteria, something less than 0.1 percent of the DNA is altered,” she said. “We started the experiments with newly emerged adult worker bees. The bacteria can persist and be effective for at least 10 days. We didn’t measure further out.”

The research team engineered one strain of bacteria to target the mites and another to target the virus. Hundreds of young worker bees in a laboratory setting were sprayed with a sugar water solution that contained the modified bacteria. By grooming one another, all the bees ingested the sugar water. They found that the bees’ immune systems became primed to protect them against DWV and ultimately kill the virus.

Compared to the control bees, those treated with the engineered bacteria were 36.5 percent more likely to survive to day 10. Varroa mites feeding on a separate set of study bees treated with the mite-targeting strain were 70 percent more likely to die by day 10 compared to mites feeding on control bees.

While the sugar water study has been successful in a lab setting, its feasibility in an agricultural hive setting has not yet been tested.

“It seems feasible to use in hives, but this hasn’t been done yet,” said Moran. “The spray works because the bees clean one another, and they ingest the sugar and the accompanying bacteria. This would also happen in a hive, but it might not be the best way to scale up for treating whole hives.”

It is still untested as to whether the modified bacteria would become permanently established in the bees’ gut structure over generations.

The GM bacteria do not present a level of threat to other organisms in the environment because they only live in the honeybee gut and do not associate with other insects or other bees. However, further research is planned to ensure its effectiveness and safety of the treatment approach in an agricultural environment.

Another benefit of the GM bacteria process is that it can be used to study bee genetics. Moran said that, while the research does not directly relate to breeding strategies, one of the most useful aspects of the results is that they provide a way to turn off genes in bees, which will be useful in bee genetic research and could eventually give useful results for future breeding approaches.

The research paper was published in the journal Science.

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