EMBL Seminars

Abstract
The study of bacterial swimming is one of the most classical and fundamental approaches to understanding motility at the cellular level. It helps us solve not only the biological puzzles of how microorganisms spread infections or communicate with each other, but also pave the way to "un-blackboxing" physical phenomenon far from equilibrium like anomalous diffusion and pattern formation. While bacterial motility has been well characterized in liquid environments, only little is known about how bacteria navigate complex environments mimicking their natural habitats like soil, mucus or tissues, where they generally face strong confinements and heterogenities. In this talk, I will discuss how we can combine experimental analysis using the soil bacterium Pseudomonas putida and active particle modeling to examine migration patterns of bacteria in disordered environments (agar gel), which leads to remarkable motility characteristics like transient subdiffusion and ergodicity breaking. Next, I will address another paradoxical question in this direction: how can bacteria perform chemotaxis in a confined environment, providing insights about the role of signaling in active transport. Finally, I will introduce a coarse-grained model that we are working on recently, where the non-reciprocal interplay of two chemicals, coupled with a Keller–Segel-like motility of microorganisms, leads to a prolific variety of patterns, ranging from different types of novel phase separation to travelling waves, breathing spots and spiral waves. ].

About the speaker
Agniva Datta is a doctoral researcher and physicist at the University of Potsdam in Germany. He works within the Institute of Physics and Astronomy and specializes in the fields of biological physics, statistical physics, nonlinear dynamics, and active matter.].

Abstract

Epigenetic components regulate many biological phenomena during development and normal physiology. When dysregulated, epigenetic components can also accompany or drive diseases. One main class of epigenetic components are Polycomb group proteins. Originally, Polycomb proteins were shown to silence gene expression. We found that this function involves the regulation of 3D chromosome folding and we found that Polycomb components can induce the formation of long-distance interactions or chromatin loops that may play instructive roles in gene regulation as well as serve as scaffolding elements that contribute to enhancer-promoter specificity. Perturbation of Polycomb components is involved in human cancer and leads to tumorigenesis in flies. Surprisingly, even upon a transient depletion followed by restoration of the full Polycomb compendium, epithelial cells lose their normal differentiated fate, continue proliferating and establish aggressive tumors, demonstrating that cancer can have a fully epigenetic origin. Similarly, transient perturbation of histone acetylation in mouse ES cells and gastruloids shows that they can record chromatin changes and that this results in cellular memory of the perturbation states. The implication of these data will be discussed.