Modified gut bug can protect honeybees against pests

Honeybees play a vital role in global food production. In the US alone, the American Beekeeping Federation estimates that honeybees contribute nearly $20 billion to the value of crop production each year. But bee colonies are suffering.

In search for a solution, a team led by Nancy Moran at the University of Texas at Austin has modified the bee gut microbiome to improve the insects’ resistance to pathogens (Science 2020, DOI: 10.1126/science.aax9039).

“This is the first time anyone has improved the health of bees by genetically engineering their microbiome,” says grad student Sean Leonard.

Terms like “colony collapse disorder” are somewhat misleading, says bee researcher Robert Paxton at Martin Luther University Halle-Wittenberg because there isn’t one single cause. Instead, bees’ elevated mortality is likely due to varroa mites and the RNA-based deformed wing virus that they carry.

To try to protect the bees from these threats, Moran’s team modified a bacteria usually found in the guts of bees, Snodgrassella alvi, to produce specific sequences of double-stranded RNA. The researchers sprayed worker bees with a sugar-water solution containing the modified bacteria. The bees swallowed the bacteria while grooming. Inside the bees’ guts, the bacteria released RNA that either activated the bees’ RNA interference–based defenses or passed to the mites, killing them.

“I think it’s great as a proof of concept,” says Kirsten Ellegaard at the University of Lausanne, who studies the honeybee microbiome. But, she cautions, the study was performed on newly emerged bees that were treated with antibiotics, making gut colonization easier. “For a honeybee that is already fully colonized, it will be a very different story, as the bacterium will need to compete with wild-type S. alvi that is already in the gut,” she says. Ellegaard adds that compared with injecting or feeding the RNA to bees directly, the microbiome could be a cheaper and more efficient way to deliver double-stranded RNA to honeybees for biological studies.