The Sterilization of Mosquitoes

Many infamous viral disease such as malaria, Zika, dengue, West Nile, and yellow fever are all carried and transmitted to new hosts by mosquitoes. For many years researchers have been looking for ways to prevent the spread of these dangerous viruses, and they often target mosquitoes. One method is to sterilize mosquitoes, thus reducing the amount of carriers. Male mosquitoes can be sterilized by infecting them with a certain bacteria (Wolbachia) that modifies their sperm. When a Wolbachia-infected male mates with an uninfected female mosquito, his sperm kills the eggs after fertilization. When the infected male mates with an infected female, her modified egg is compatible with his modified sperm, and the eggs survive.

While this sterilization method is being used, scientists didn't really understand all the mechanisms underlying how it works. To understand why this bacteria causes sterilization, a group of scientists from Vanderbilt University pinpointed two genes in Wolbachia called cifA and cifB and inserted them into male fruit flies. They found that these males could no longer reproduce with normal female flies, but just like in the mosquitoes, they could still reproduce with infected females. The infected females "rescue" the modified sperm which reminded scientists at the Yale School of Medicine of antidotes and toxins. They used simple yeast cells to test this hypothesis and put the "toxin" gene into the yeast, which resulted in the yeast cells dying. On the other hand, when they put both the "toxin" and "antidote" genes into the yeast, they survived.

These experiments in both fruit flies and yeast mirror what is happening in mosquitoes. Since the discovery of this gene pair, researchers have considered adding extra copies of these genes into bacteria, creating a "super Wolbachia" that more potently sterilizes the mosquitoes. Yet, this could "essentially crash the population" said coauthor of the fruit fly study Seth Bordenstein. While the creation of bacteria with multiple copies of the genes has not yet been attempted, this research unveils the genes responsible for the sterilization of mosquitoes, and helps fight against the spread of viral diseases.

Link to news article: https://www.sciencenews.org/article/bacteria-genes-offer-new-strategy-sterilizing-mosquitoes?mode=topic&context=87