Popular Science Presentation

Microorganisms that cannot be grown in pure cultures make up a large part of the biomass and genetic diversity on earth, but because of the difficulties in studying them much of their unique properties and their genetic diversity has remained unknown. Among these are symbiotic microorganisms associated with eukaryotes, many of which have a large impact on both disease and health of their hosts and where the interactions have lead to intriguing and important evolutionary novelties and adaptations for the organisms involved.

Arthropods are one of the most species rich of all eukaryotic phylum’s and part of the explanation for their success comes from the ability to exploit new niches, by for example adapting to unusual and nutrient low dietary regimes, such as vertebrate blood and plant sap. In order to do so, many insect species have developed tight symbiotic relationships with microorganisms such as bacteria and fungi. Some of these symbionts are therefore necessary for the host to survive, but many are not strictly required for host survival and the reason for their presence is not well understood.

Most of our work is focused on the symbiotic bacterium Wolbachia that lives inside the cells of many different arthropod species and often affects their reproduction. Wolbachia can for example change males into females, selectively kill male embryos and induce asexual reproduction so that only female offspring are produced. Why? Because Wolbachia is transmitted from mothers directly to the offspring via the egg, and hence Wolbachia needs to infect females in order to spread. In order to prevent uninfected offspring from being produced, Wolbachia can also sterilize infected males if they try to mate with an uninfected female. This sterility effect is referred to as cytoplasmic incompatibility (CI), and is the focus of much of our research as we one of our goals is to find out which Wolbachia genes are responsible for causing it.

To reach this goal and to learn more about the natural diversity of symbiotic bacteria, we sequence the genomes of many different Wolbachia strains as well as other bacteria that live in symbiosis with insects and arthropods and compare them to each other. Using this method we can learn more about how they have adapted to a symbiotic lifestyle and hopefully also how they affect their hosts.