Engineered symbionts activate honey bee immunity and limit pathogens

In this study the bacterium Snodgrassella alvi, known as a symbiotic bacterium in the gut of honey bees, was genetically modified to produce specific dsRNAs to induce RNA interference (RNAi) in varroa mites and the deformed wing virus (DWV). Apparently honey bees that contain genetically modified S.alvi are protected from varroa and DWV.

RNAi is a natural process using double stranded RNA molecules to induce gene silencing in the host by blocking the translation or by degradation of like-sequenced mRNA. Researchers integrated the RNAi machinery to S. alvi so that these bacteria produce specific dsRNA that were designed against essential genes of varroa or DWV. From the gut, the dsRNA is spread by the hemolymph (blood of insects) through the whole body of the bees. Mites infesting bees, that contain the genetically modified bacterial strain, take up the dsRNA and thereby the RNAi response of the mites is activated. This leads to the blocking of essential processes of the mites. Generally, microbiome engineering is used to alter microbes in a way that they increase the resistance against pathogens or pest of their host. Genetically altered (and wildtype) S. alvi are transmitted via the direct contact of honey bees. Thus, it is important to investigate whether the genetically engineered bacteria can also be transmitted to other insects an bee species. Until now, S. alvi was only found in honey bees. Furthermore it needs to be studied if genetically modified S. alvi is capable to survive outside of the gut to exclude the possiblity of unwanted spread.