PhD defence: Microbial Evolution at Multiple Scales

Microbes are life forms that are too small to see with the naked eye, such as bacteria and viruses. They are found in all habitats on earth, and also greatly influence human life. Some microbes cause diseases, while others are beneficial to our health. For instance, the bacteria in our gut help to digest food. Microbes evolve fast, which allows them to quickly adapt to new circumstances; the rapid evolution of resistance to antibiotics is a prime example of this. To understand, and possibly control, the life of microbes, we hence should always take their evolution into account.

In evolution, populations of organisms adapt to their environment through inheritance and natural selection. An organism’s environment is however not static: it varies over space and time. Which features are evolutionarily favourable hence depends on the time and spatial scale considered. In our research, we use mathematical and computational models to study how the evolution of microbes depends on processes at different scales. The use of models allows us to study many different evolutionary scenarios in short times.

Using these models, we show how HIV can evolve to spread well in human populations, how a communication system between viruses can evolve, and how bacteria can use information about the presence of other bacteria nearby to attack their competitors. Lastly, we introduce a general mathematical framework that measures the effects of spatial structure on natural selection. Taken together, this research helps us understand the wonderful world of microbes.