Biofilms are dense multicellular communities of bacteria that form on surfaces. Biofilms are widespread in nature and implicated in many acute medical and industrial problems. Previously we discovered that mature biofilms of B. subtilis bacteria grown on agar surfaces possess a network of interconnected channels which facilitate the transport of liquid within the biofilm. We now turned to the early stages of biofilm development and want to understand how biofilms form. Together with our collaborators, group of Nicolas Biais (CUNY, USA), we consider the self-assembly of N.gonorrhoeae bacteria microcolonies. These bacteria cause one of the most common sexually transmitted diseases gonorrhoea where the microcolonies represent the infectious unit of the disease. In a series of works, we demonstrated that cells use long retractile filaments called pili to attach and move on surfaces as well as to attach to other cells and self-assemble into spherical colonies containing thousands of cells. Here we applied a variety of statistical physics approaches from modeling to the analytical framework of kinetic and hydrodynamic descriptions. Recently we were able to create an in silico model of the bacterial colony with explicit pili dynamics and interaction forces that recapitulates our experimental observations on various space and time scales. We could show that the pili forces were responsible for the emergence of heterogeneous cell motility within large micro-colonies of essentially identical cells. The presented figure illustrates the cross-section of the micro-colony where the mutant cells (red) that are not able to retract pili get segregated to the outside of the wild-type cells (yellow).
Our next step is to relate the force distribution within the colony (which can now be obtained in our model) to the gene expression pattern (which can be measured experimentally) and thus test for the hypothesis of mechanosensing in bacterial communities.
Pili mediated intercellular forces shape heterogeneous bacterial microcolonies prior to multicellular differentiation;
W. Pönisch, K.B. Eckenrode, K. Alzurqa, H. Nasrollahi, C. Weber, V. Zaburdaev and N. Biais, Scientific reports 8 (1), 16567 (2018)
Relative distance between tracers as a measure of diffusivity within moving aggregates; W. Pönisch, V Zaburdaev
The European Physical Journal B 91 (2), 27 (2018)
Multiscale modeling of bacterial colonies: how pili mediate the dynamics of single cells and cellular aggregates; W. Poenisch, C. A. Weber, G. Juckeland, N. Biais, and V. Zaburdaev, New Journal of Physics 19, 015003 (2017)
Pili-Induced Clustering of N. gonorrhoeae Bacteria; J. Taktikos, Y.T. Lin, H. Stark, N. Biais, and V. Zaburdaev, PLoS ONE 10: e0137661 (2015)
Formation and dissolution of bacterial colonies; C.A. Weber, Y.T. Lin, N. Biais, and V. Zaburdaev, Phys. Rev. E 92, 032704 (2015)
Uncovering the Mechanism of Trapping and Cell Orientation during Neisseria gonorrhoeae Twitching Motility; V. Zaburdaev, N. Biais, M. Schmiedeberg, J. Eriksson, A.-B. Jonsson, M. P. Sheetz, and D. A. Weitz, Biophys J 107, p1523–1531, (2014)