Have you ever thought of yourself as an ecosystem? Or even, a planet, hosting trillions of inhabitants! If not, get used to the fact that you are one! Each and every one of us provides a home for millions of microbes that live inside our body, and on our skin. Some of these tiny creatures just use us as their living space, without affecting us. Some do us harm. Many, however, benefit us immensely. They help us digest food and fight off diseases, and might even be important in keeping our brains healthy. The community of microbes in our body is called our microbiome.
Humans are not unique in having microbiomes! Insects – like fruit flies – also host microbial communities. We examined the microbiomes of different fruit fly populations originating from six different places across Europe. We showed that their microbiomes were different, even though all flies had eaten the same food over the past four years. We also examined the effect of microbes on fruit fly resistance to parasite attack. In some populations, we found evidence for this, but for other populations we did not find a clear connection.