Loading...
Files
Date
Publisher
Philipps-Universität Marburg
Supervisors
Abstract
Microbial communities often exhibit complex spatial structures that are important for their
functioning, ecology and evolution. While the role of biochemical interactions has been extensively
studied, it is unclear how physical interactions contribute to the structuring of multispecies
and phenotypically diverse bacterial communities.
Here, we investigate the physical effect of motility, a key bacterial trait, on the spatial
organization of complex communities, using binary bacterial mixtures as a minimal model
system, where one component is motile and the other is not. We observe that large spatial
heterogeneities in the density of non-motile cells arise under the influence of the motile cells,
which themselves remain homogeneous. Using a combination of experiments and quantitative
modelling, we show that this patterning results solely from physical interactions and relies
on two key ingredients: by swimming in circles on the surface, the motile bacteria generate
recirculating hydrodynamic flows that advect non-motile cells, and the breaking of vertical
symmetry by gravity allows local density accumulation. As the configuration of the motile cells
swimming on the surface rearranges, the advection landscape also does, making the density
patterns fluctuate. This new non-equilibrium mechanism for pattern formation in bacteria
belongs to a different class compared to previous models for self-organization in self-propelled
systems, which rely on localized traffic jamming in two dimensions. It is instead similar to
fluctuation-dominated phase ordering in active nematics.
As these density patterns form over a wide range of biologically relevant densities of both
phenotypes, we also investigated their effect on the aggregation of adherent non-motile cells and
on biofilm formation. We found that the activity of the motile cells enhances the aggregation
of non-motile bacteria and that adhesive motile cells promote the formation of complex, threedimensional
biofilm structures, suggesting that motility, together with the ability of motile cells
to aggregate, is important for the early stages of biofilm formation.
These results show how the activity of motile species can shape the spatial organization of
complex microbial communities and highlight the importance of studying the physical interactions
in these communities.
Review
Metadata
Contributors
Supervisor:
Dates
Created: 2024Issued: 2024-09-30Updated: 2024-09-30
Faculty
Fachbereich Biologie
Publisher
Philipps-Universität Marburg
Language
eng
Data types
DoctoralThesis
DDC-Numbers
570
show more
Espada Burriel, Silvia (0009-0003-5963-2838): Emergent spatiotemporal structures in bacterial binary mixtures. : Philipps-Universität Marburg 2024-09-30. DOI: https://doi.org/10.17192/z2024.0463.