We focus on the physics of bacterial systems. At the level of single molecules we investigate the mechanism of force generation in bacteria. How are directed movement and force generated at the molecular scale? How do interbacterial forces govern biofilm structure? We are particularly interested in bacterial motors involved in motility and horizontal gene transfer. At the population level, we investigate the evolutionary significance of these molecular motors. What are costs and benefits of horizontal gene transfer? How do interaction forces evolve in biofilms? In our group, physicists, biologists, and biochemists work in close collaboration using a combination of tools from nanotechnology, image analysis, molecular biology, and genomics.

Most bacterial species form structured communities called colonies or biofilms. Structure, viscosity, and surface tension of these colonies are governed by various physical interactions between bacteria. They include steric repulsion, bridging attraction, depletion forces, and osmotic pressure. Bacteria actively tune these interactions by adjusting the production level of proteins and polymers at the cell surface. How do changes in surface proteins affect attractive forces between bacteria? How do these forces control colony structure and dynamics? We combine laser tweezers technology with advanced microscopy, image analysis, and molecular biology to address these questions. [more ...]

This project is associated with the IHRS school BioSoft.

Bacteria can adapt to stresses by aggregating into colonies and biofilms. Within these aggregates bacteria are protected against killing by antibiotics, phages, or predators. How does aggregation confer tolerance against antibiotics? Are physical properties of colonies correlated with bacterial survivability? We address these questions in the framework of the Center for Molecular Medicine Cologne. We develop tools for 3D live-cell tracking, combine them with transcriptomics, and apply them to a clinical strain collection of the human pathogen Neisseria gonorrhoeae. [more ...]

In their natural habitats, bacteria live in close contact with other species. Genomic studies reveal plentiful evidence of gene transfer across different species. However, little is known about its rates and fitness effects. What are limiting factors of cross-species gene transfer? Can the entire genome be exchanged between two species? How does gene transfer affect bacterial fitness? While gene transfer can benefit bacteria during adaptation to new niches, it also bears the potential of reducing fitness by introducing maladapted genes. In the frame of the CRC 1310, we study these trade-offs by combining experimental evolution with genomics, transcriptomics, and molecular biology. [more ...]

Transport of macromolecules through nanometer-sized membrane pores is a ubiquitous theme in cell biology and an interesting problem in physics. For example, during gene transfer by transformation, bacteria take up micrometer-long DNA from the environment through nanometer-sized pores into the cell envelope. To make DNA uptake efficient, an energy consuming molecular machine powers the uptake process. How does the DNA uptake machine work? How does it use chemical energy to generate directed movement of the DNA molecule? We tackle these questions by combining laser tweezers technology with molecular biology. [more ...]

Biofilms are considered ideal reaction chambers for horizontal gene transfer and development of multi-drug resistance. Yet, the rate at which genes are exchanged within biofilms and the factors that govern the exchange rate are unknown. How fast do DNA molecules move within biofilms? How fast do genes spread within biofilms formed by different bacterial strains or species? Single molecule fluorescence microscopy and advanced image analysis are developed to better understand gene transfer in biofilms. [more ...]