Scientists at the University of Texas at Austin report in the journal Science that they have developed genetically modified bacteria tohoney beesto protect against a deadly trend known as colony collapse disorder (CCD). The modified bacteria that live in the guts of bees act like a “living vaccine” against two of the main causes of colony collapse: Varroa mites and “deformed wing virus” (DWV), which often occur together.
Honey bees have a remarkable gut microbiome, as well as an antiviral defense mechanism called RNA interference (RNAi), which helps fight off certain viruses (so-called RNA viruses).
Jeffrey Barrick, a microbial evolutionary biologist at the University of Texas (Austin), and his colleagues decided to see whether they could recruit bacteria that live in the honey bee's gut to produce RNA that the mite or virus can do causes them to destroy some of their own genes. While humans have thousands of species of gut bacteria, all honeybees have the same six to eight gut microbes.
Barrick's graduate student Sean Leonard figured out how to genetically modify one of these bacteria, Snodgrassella alvi, so that it continuously produces RNA that matches the genetic material he wants to break down: genes that are essential for the survival of the mite or virus are. He then fed groups of up to 20 bees the bacteria before exposing them to the mites or virus.
For the mite test, the researchers tracked the fate of the parasitic pests. The mites are about 70 percent more likely to die within 10 days when feeding on bees with the new gut microbes than control bees.
The virus tests also looked promising. Bees inoculated with protective bacteria had a 37 percent higher survival rate 10 days after exposure to the deformed wing virus.
The modified intestinal bacterium remains in the honey bee's intestine for at least the duration of the experiments (15 days) and provides a consistent supply of antiviral RNA. And because adult bees feed developing bees, they may be able to pass on these beneficial gut microbes to the next generation, Barrick says.
The researchers believe their method could one day be used in agriculture because the genetically modified bacteria are easy to grow, vaccinating bees is easy, and the gut bacteria are unlikely to spread beyond the bees.
Another advantage of the approach is that researchers can use it as a tool to study bee genetics. The genetically modified bacteria can provide insights into how the bee genome works and potentially enable new breeding strategies to produce more robust bee colonies.
Honey bees play an enormous role in global food production. Without honey bees, dozens of crops, from almonds to berries to broccoli, would either disappear or produce significantly less food. According to a national survey, beekeepers in the United States lost nearly 40% of their honey bee colonies last winter. This is the highest rate recorded since the survey began 13 years ago.
Weitere Informationen: “Engineered symbionts activate honey bee immunity and limit pathogens”Science (2020).
