I lead the Microbial Community Assembly group at Eawag. Our research is inspired by the extraordinary levels of biodiversity that are typically present within microbial communities. For example, a single liter from a lake, a river, or the aeration basin of a wastewater treatment plant is estimated to contain many thousands of microbial strains and to express tremendous numbers of functional traits. These extraordinary levels of biodiversity underscore two ecological questions that we are particularly interested in:
- Why are microbial communities so biodiverse? What are the underlying mechanisms that promote biodiversity and enable the apparent co-existence of many thousands of microbial strains?
- Is biodiversity important for the provision of ecosystem services? If so, can we predict how differences or changes in biodiversity are likely to affect the provision of those service?
We investigate the mechanisms that promote biodiversity using experimental systems. The central hypothesis is that different metabolic processes are in biochemical conflict with each other, thus causing those processes to be more effectively performed by different microbial strains than by the same strain.
One possible consequence is the emergence of biodiversity. To test this hypothesis, we experimentally measure biochemical conflicts between different metabolic processes and track their cellular fate over evolutionary time. The ultimate goal is to improve our general understanding about how biodiversity is promoted and maintained within the natural environment.
We investigate the relationship between biodiversity and the provision of ecosystem services using environmental systems. The central hypothesis is that biodiversity is more important for the provision of specialist ecosystem services (i.e. services that are performed by only a few strains) than for generalist ecosystem services (i.e. services that are performed by many strains). To test this hypothesis, we measure the provision of many different ecosystem services in parallel and quantify their relationships with biodiversity. We then test whether the shapes of the relationships depend on the degree of specialization of each ecosystem service. The ultimate goal is to improve our general understanding about why biodiversity is more important for the provision of some ecosystem services than for others.
Current Research Projects
Metabolic specialization and the causes of diversity in microbial ecosystems. Johnson DR (lead PI). Swiss National Science Foundation. 2014-2017.
Design and systems biology of functional microbial landscapes (MicroScapesX.ch). van der Meer JR (lead PI), Hazimanikatis V, Johnson DR, Or D, Que YA. SystemsX.ch program of the Swiss National Science Foundation. 2014-2018.
Microbial resource management and engineering in the urban water cycle (MERMAID). Smets B (lead PI), 13 others (including Johnson DR). European Commission, Marie Curie Actions - Initial Training Network. 2014-2017.