Collective membrane potential dynamics in bacterial colonies

• Applicant: Professorin Dr. Berenike Maier
• Subject Area: Biophysics ; Medical Microbiology and Mycology, Hygiene, Molecular Infection Biology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 503746438

Bacteria generate an electrical potential difference across their inner membrane: they are electrically polarized. Polarization plays important roles in ATP synthesis and membrane transport. Recent studies have shown that polarization in planktonic bacteria is strikingly heterogeneous and dynamic. However, little is known about polarization dynamics in spatially structured bacterial communities. We have discovered that spatial polarization patterns arise in colonies of Neisseria gonorrhoeae, which travel in waves through the colony. In the first phase of the project, we were able to show that the transition to this collective polarization marks the beginning of differentiation into subpopulations with different growth rates and antibiotic tolerance. We were able to show that the polarization pattern is determined by the local oxygen gradient within the colony. In the next phase of the project, we want to understand the molecular mechanisms and biological functions of the collective polarization dynamics. First, we will search for ion transporters and ion channels that influence the polarization dynamics. Deletion strains of these transporters or channels will facilitate functional characterization. Next, we want to link the polarization dynamics with the morphological dynamics of the colonies. In particular, we will use a combination of laser tweezers, single-cell tracking and particle image velocimetry to test the hypothesis that transient hyperpolarization reduces the cohesive forces in the centre of the colony and thus triggers a global restructuring of the colony. Another question will be how the transition from aerobic respiration to denitrification affects the polarization dynamics. Preliminary experiments indicate heterogeneity between individual cells and between individual colonies in polarization and growth. To understand this heterogeneity, we will develop reporter strains for the expression of genes involved in both metabolic pathways. Finally, we will test the hypothesis that the heterogeneity enables a fitness trade-off between growth and antibiotic tolerance. The project will make an important contribution to our understanding of collective phenomena in bacterial electrophysiology. Within the priority program, we will test the generalization to other bacterial species.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2389: Emergent Functions of Bacterial Multicellularity