Engineered Bacteria Against Varroa And Viruses

The production of honey (and other hive products) and its role as pollinator par excellence have made the European bee of enormous economic and environmental value to the survival of our species and the entire planet. Attention on the threats to this species is growing more and more. Among the beekeepers' black beasts is a mite, the Varroa destructor, which not only has a direct effect on the survival of the bees it infects, but is also a vector of countless viruses. A study published in Science late last week suggests an approach to combat Varroa, based on genetically engineered bacteria capable of inducing an immune response. In addition to protecting bees, this approach would also allow a better study of their genome.

The authors of the study, a group of researchers from the University of Texas at Austin, worked on a bacterial strain that is part of the bee microbiome. Using genetic engineering techniques, they ensured that one strain could activate a response against the mite and another against the deformed wing virus, of which Varroa is a vector. The more mites feed on bees, the more the virus spreads, making bees increasingly vulnerable to various pathogens in the environment. The researchers had the bees ingest engineered bacteria by placing them in a solution of water and sugar. Once established in the gut, the new bacteria proved capable of acting against the virus and Varroa. In the case of the latter, in particular, the effect is that of self-destruction: the mite in fact feeds on the bee's tissues and thus also ingests the modified bacteria.

The implication of such a method is direct and it is also the first time that the microbiome of bees has been genetically engineered to improve their health. In tests, bees treated with the engineered bacterium showed a 36.5% greater chance of survival after 10 days than bees in the control group. At the same time, mites feeding on the bees that had ingested the engineered bacterium were 70% more likely to die by day 10 than mites feeding on the control group bees. The tested method, as Robert Paxton explains in an article in Science, besides proving effective, could have the advantage of persisting in the colony due to possible genetic transmission from larva to pupa.

The approach studied may also be useful for delving into the genetics of bees, silencing certain genes or considering using the same technique to help bees detoxify certain pesticides, which are also involved in colony damage. At the same time, the new work raises the question of the possibility of "escape" of genetically modified bacteria into the environment. The research was conducted following strict biocontainment protocols, but by the time the technique is applied to colonies reared around the world, the bacterium could be transferred to other insects. However, the bacteria used are highly specialised to live in the intestine of bees, outside of which they do not survive for long and their protective effect is against a virus that can only reproduce on this insect. However, further research and careful evaluation will be needed to see whether the technique can be applied.