Bacteria from the microbiome of honeybees have been genetically modified to protect the insects against lethal infections, which could help with the recovery of hives.
European honeybees (Apis mellifera) are vital pollinators, but numerous factors such as disease and pests are slashing their numbers. A major concern for most bee species is colony collapse disorder, a global phenomenon that has wiped out large numbers of hives in recent years.
Sean Leonard and his colleagues at the University of Texas at Austin used a technique called RNA interference (RNAi) to tackle two of the biggest global killers of bees: parasitic varroa mites and deformed wing virus (DWV). Both DWV and varroosis 鈥� the disease caused by the mites 鈥� are closely linked to colony collapse.
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The team engineered a bee gut bacterium called Snodgrassella alvi, a normal part of the bee microbiome, to express double-stranded RNA targeting either the DWV genome or essential genes in varroa. Many organisms naturally respond to such strands by switching off genes with complementary sequences, making it useful for gene editing.
Though the RNA can be injected into the bees directly, a large amount of it would need to be made. This is expensive and 鈥測ou can鈥檛 inject 80,000 individual bees鈥�, says Leonard, which is about the number in a hive.
Instead, his team dunked 980 honeybees in a sugar solution containing the engineered S. alvi. The bees then ingest the bacteria when they clean the solution off each other. When a bee encounters the virus, its RNAi response is triggered to switch off the viral genes, while mites feeding on the bees can take up the RNA and die.
The team found that in bees infected with DWV, those with an engineered microbiome had about a 40 per cent survival rate after 10 days compared with around 25 per cent for control bees. Mites also died more quickly when feeding on bees with engineered microbiomes, reducing the risk of varroosis.
Using engineered S. alvi to supply the RNA is beneficial because the bacteria can continuously produce RNA in the bees鈥� guts as they grow. The team found that RNA production inside the bees lasted for up to 15 days 鈥� the duration of the experiments 鈥� but more testing is needed to see whether it could last longer, says Leonard.
鈥淲hat really excites me is that this is a potential tool that scientists can use to better understand honeybee health and biology,鈥� says Dennis vanEngelsdorp at the University of Maryland. But although it works well in the lab, we need to be cautious about extrapolating to entire hives, he says.
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