Graduate Students Mini Symposium IV-2023

Program

13:15 h Shan Jiang - PG Yuan
The inhibitory mechanism of a small protein reveals its role in antimicrobial peptide sensing

Small proteins have been shown to have vast diversity and predominant regulatory functions in biological processes across all domains of life. However, their mechanisms of action remain largely elusive. In this study, I investigate the mechanism of the small protein, MgrB. It interacts with PhoQ sensor kinase, rearranges its conformation, represses its kinase activity and regulates bacterial response to environmental changes. Particularly for antimicrobial peptides, MgrB is required for bacteria to have a selective response to this host-exclusive stimulus. Our findings underline the importance of a small protein in bacterial fitness and drug resistance.

13:45 h Silvia Espada Burriel - PG Colin
Density fluctuations in bacterial binary mixtures

In nature, motile and sessile microorganisms interact to give rise to complex community organization. Here, we investigate the role of physical interactions in these processes by studying the physical behavior of binary mixtures of motile and non-motile Escherichia coli bacteria. We report a novel phenomenon by which non-motile bacteria form large density fluctuations when mixed with motile bacteria. We systematically explored this phenomenon in microfluidics and microscopy experiments and with simulations. Our results highlight the importance of the circular swimming of motile cells that localize at surfaces, hydrodynamic interactions, and sedimentation of the non-motile cells under gravity.

14:15 h Yannick Gietz - AG Bischofs-Pfeifer
What spore pH and biophysics can tell us about spore germination

Maintenance and release of electrochemical gradients are key to information processing in certain cells and may play a role in bacterial spores. However, conventional electrophysiological methods may not be applicable to spores due to their small size and complex architecture. Here, we introduce a novel, non-invasive and microscopy-based approach to monitor changes in internal spore pH. We demonstrate that dormant Bacillus subtilis spores passively dissipate an electrochemical proton gradient within hours. We also show that upon sensing nutrient germinants, spores generate a proton motive force resulting in an increase in their internal pH. We are currently investigating the generation of the proton motive force upon spore germination by using knock-outs.