Scientists have genetically engineered strains of bacteria to help bees fight pests and pathogens that are leading to a widespread deadly trend known as colony collapse.
The engineered bacteria live in the guts of honey bees and act as biological factories, pumping out medicines protecting the bees against two major causes of colony collapse: Varroa mites and deformed wing virus, said the study published in the journal Science.
Hopeful of agricultural use
The researchers from The University of Texas at Austin in the US who engineered the strains of bacteria believe their method could one day scale up for agricultural use because the engineered bacteria are easy to grow, inoculating the bees are straightforward and the engineered bacteria are unlikely to spread beyond bees.
"It has direct implications for bee health," said Nancy Moran, Professor of Integrative Biology at the university and the primary investigator on the study. "This is the first time anyone has improved the health of bees by genetically engineering their microbiome," added the first author of the study, Sean Leonard.
Varroa mites and deformed wing virus often come together. As the mites feed on bees, they can spread the virus, while also weakening the bees and making them more vulnerable to pathogens in the environment.
To address each problem, the team engineered one strain of bacteria to target the virus and another for the mites. Compared with control bees, the bees treated with the strain of bacteria targeting the virus were 36.5 percent more likely to survive to Day 10. Meanwhile, Varroa mites feeding on another set of bees treated with the mite-targeting strain of bacteria were about 70 percent more likely to die by Day 10 than mites feeding on control bees.
Like humans, honey bees have an ecosystem of bacteria in their guts called a microbiome and also an antiviral defence mechanism called RNA interference (RNAi) that helps the body fight off certain viruses, called RNA viruses. When an RNA virus is introduced, it produces molecules called double-stranded RNAs that a healthy cell detects, triggering an RNAi immune response.
To promote a helpful RNAi response to viruses in bees -- and trigger a lethal RNAi response in the mites -- the team introduced modified bacteria to hundreds of bees in a laboratory setting. Sprayed with a sugar-water solution containing the bacteria, the bees groomed one another and ingested the solution.
Young worker bees key
The team found inoculating young worker bees with the engineered bacteria led the bees' immune systems to be primed to protect them against the deformed wing virus, which is an RNA virus, and caused the mites' own immune systems to fight against and ultimately kill them.
The type of bacteria used are highly specialized to live in the bee gut, can't survive for long outside of it and are protective for a virus that strikes only bees. Still, further research will be needed to determine the effectiveness and safety of the treatments in agricultural settings.