I promised more about Wolbachia, and here it is. Quick recap: Wolbachia is a type of bacteria that lives within the cells of many insects and other arthropod species.
Wolbachia has all sorts of possible effects ranging from parasitism to symbiosis. Anopheles mosquitoes, the bugs that carry malaria and thus kill hundreds of thousands of people every year, are naturally uninfected with Wolbachia, but scientists have been investigating ways to introduce Wolbachia into them so as to prevent malaria transmission. One recent study found that, in addition to suppressing malaria transmission by mosquitoes, a certain strain of Wolbachia killed many of the infected mosquitoes, but only after they had had a blood meal.
Now, the pathogen literature is not something I normally read; I stumbled across this research on a science fiction blog. This article I’ve linked to takes a rather cute approach to this study by suggesting that it could be used to kill vampires in the event that they begin to plague the human race. Commenters on that article raised the spectre of unintended side-effects of infecting people with Wolbachia. Well, commenters, here is what you (thought you) wanted to know:
Imagine you’re a Wolbachia cell. You’re inside the cell of an insect, say a mosquito. That mosquito spreads you (and your descendents) to other mosquitoes not by biting them or sneezing on them, but by reproducing: since you’re already inside the mosquito’s cells, you just get packaged into their baby-making cells. Well, not necessarily—if you’re in a male mosquito, you’re screwed, because you just won’t fit into a tiny little mosquito sperm. If you’re in a female mosquito, though, you’re in luck (that’s right, you’re maternally inherited). But you’re a clever Wolbachia and you’re thinking not just of your kids, but of your grandkids (which will all also be your clones because you’re a bacterium!). You don’t want any of your descendents to end up in male mosquitoes. What can you do to prevent this? Let’s brainstorm:
- kill all the male offspring of the female you’re infecting
- turn the male offspring into functional females
- make your host into a parthenogen, i.e. make her reproduce asexually!
Guess what! Wolbachia can do all of the above! SF writers, have at it.
Hughes, G., Koga, R., Xue, P., Fukatsu, T., & Rasgon, J. (2011). Wolbachia Infections Are Virulent and Inhibit the Human Malaria Parasite Plasmodium Falciparum in Anopheles Gambiae PLoS Pathogens, 7 (5) DOI: 10.1371/journal.ppat.1002043