Collective membrane potential dynamics in bacterial colonies

•  Prof Dr Berenike Maier Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Institut für Biologische Physik.

Structured populations of Bacillus subtilis coordinate their metabolism by electrical communication. Currently, it is unknown whether other bacterial species synchronize their electrochemical behaviour.

We found that within spherical colonies formed by Neisseria gonorrhoeae, bacteria hyperpolarize at the center and subsequently, a shell of hyperpolarized cells travels radially towards the periphery of the colony. This hyperpolarization is followed by depolarization at the colony center. In this project, we aim to discover triggers for hyperpolarization, the mechanism of collective propagation of hyperpolarization, and its relation to growth arrest and related consequences on population fitness. Specifically, we will correlate growth arrest at the colony center with membrane potential. To this end, we will combine our recently established method for characterizing the growth rate with spatio-temporal resolution with tools for characterizing the membrane potential. Then, we aim to investigate two putative triggers of hyperpolarization. We will assess whether the depletion of oxygen or a nutrient causes hyperpolarization.

Furthermore, we will test the hypothesis that build-up of mechanical pressure at the center of the colony limits growth and causes hyperpolarization. We will vary the pressure by tuning the attractive force between gonococci in the colony. Attractive forces will be tuned by genetically modifying type 4 pili and characterized by laser tweezers.

Finally, we will address the question whether cell-to-cell communication is required for the propagation of hyperpolarization. To this end, we will investigate the spatio-temporal dynamics of the hyperpolarization wave in different colony structures. In the long term, it will be important to identify the ion channels responsible for hyperpolarization and to address the fitness effects of collective changes in membrane potential.

Researcher(s)

Paul Schiefer (PhD Student) Dr Marc Hennes

About Us

We are a multidisciplinary group where physicists, biologists, and biochemists work in close collaboration using a combination of tools from nanotechnology, image analysis, molecular biology, and genomics. Our focus is the physics of bacterial systems. At the level of single molecules, investigating the mechanism of force generation in bacteria.

• How do interbacterial forces govern biofilm structure?

Research Focus

We are particularly interested in bacterial motors involved in motility and horizontal gene transfer. Investigating the evolutionary significance of these molecular motors at the population level.

• What are the costs and benefits of horizontal gene transfer?
• How do interaction forces evolve in biofilms?

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