Population dynamics under flow

Aim: Simulations and experiments on populations of organisms living in aquatic environments and growing under flow conditions.

Ocean, rivers and lakes are natural environments for many living organisms. In these ecosystems they reproduce, compete for food, swim and die. The presence of a flow can have a strong effect on their dynamics both at individual and population scales and it is not clear yet how to describe the dynamics of systems where both transport and growth play a role. We are mainly interested in a population of individuals expanding by growth in new territories and how the propagation speed is changed by the flow. Another question is how different species compete in such environments and, for example, how the extinction probability depends on the fluid dynamics.

Picture of a microfluidic device on a fluorescent microscope for the growth of colonies of bacteria under controlled flow conditions.

Population dynamics can be studied with numerical models but also experiments are performed with bacteria inside microfluidic devices. Bacteria are injected in micro-channels and observed for many days using microscopy equipment. We investigate how they colonize the channels and the way the colony propagates both upstream and downstream under flow. In order to measure these phenomena, the bacteria are modified and made fluorescent. It is possible to modify them in various ways so that they can be detected using different optical filters since they emit different colors. In this way also the competition between different growing species can be measured in space and time.

Growth of a colony of bacteria on a gel surface (agar plate). Two species are labelled as two different colors in order to show how they compete while expanding from the inoculation point.

Group members

Francesca Tesser, Herman Clercx, Federico Toschi

Jos Zeegers (group MTP)