Abstract
As individuals, bacteria are greatly underappreciated. By tradition, they have been analyzed and understood as populations, without regard for the natural variation that exists among the individuals of a given population. This approach clashes with the central concept of individual-based ecology (IBE), which states that individual variation actually is a major driver of population structure and functioning. IBE offers a theoretical framework for explaining population- and ecosystem-level patterns in nature as a result of the interactions of individuals with each other and their environment. While microbial ecologists have yet to fully exploit the potential of IBE, there is a growing appreciation for the fact that little is known about how an individual bacterium perceives its habitat and how this perception ultimately influences its behavior and fate in a bacterial community. I propose to address this concept of bacterial individuality from an IBE perspective, using the phyllosphere, or plant leaf surface, as a model ecosystem. Habitat to highly diverse microbial communities, the phyllosphere offers many information-rich patterns in need of explanation, such as the aggregation of bacteria on the leaf surface and the leaf-to-leaf variability in bacterial abundances. To explain these patterns, I will make use of the phyllosphere?s unique amenability to experimental manipulation by applying novel and existing tools for the interrogation of individual bacteria as they colonize the leaf surface. In a parallel and complementary approach, I will use individual-based modeling, an essential tool in IBE, to simulate the colonization process, from immigration to aggregation. By combining both experimental and modeling approaches, this work will expose key properties of bacteria and leaf surfaces that underlie the observed patterns in bacterial behavior in the phyllosphere. Moreover, it will reinforce the status of the phyllosphere as an ecosystem with great service to the testing of universal theories and concepts in ecology.
Netherlands