Surfing on protein waves: modeling the bacterial genome partitioning
Résumé
Controlled motion and positioning of colloids and macromolecular complexes in a fluid, as well as
catalytic particles in active environments, are fundamental processes in physics, chemistry and
biology. Here we focus on an active biological system for which precise experimental results are
available. Our work is fully inspired by studies of one of the most widespread and ancient
mechanisms of liquid phase macromolecular segregation and positioning known in nature:
bacterial DNA segregation systems. Efficient bacterial chromosome segregation typically requires
the coordinated action of a three-component, fueled by adenosine triphosphate machinery called
the partition complex. We can distinguish two steps: (i) a process of phase transition [2,3] to
built a membraneless region of high protein concentration (partition complex) (ii) the action of
molecular motor action upon the complex to create a chemical force.
We present a phenomenological model [1] accounting for the dynamics of this system that is also
relevant for the physics of catalytic particles in active environments. The model is obtained by
coupling simple linear reaction-diffusion equations with a volumetric chemophoresis force field
that arises from protein-protein interactions and provides a physically viable mechanism for
complex translocation. This description captures experimental observations: dynamic oscillations
of complex components, complex separation and symmetrical positioning. The predictions of our
model are in agreement with and provide substantial insight into recent experiments. From a non-
linear physics view point, this system explores the active separation of matter at micrometric
scales with a dynamical instability between static positioning and travelling wave regimes
triggered by the dynamical spontaneous breaking of rotational symmetry. We also discuss the
phase transition mechanism giving rise to macromolecular assembly of proteins. Our predictions
are compared to Super Resolution microscopy and microbiology experiments [1,2,3].
[1] Walter J.-C., Dorignac J., Lorman V., Rech J., Bouet J.-Y., Nollmann M., Palmeri J., Parmeggiani
A. and Geniet F., Phys. Rev. Lett. 119, 028101 (2017).
[2] Debaugny R., Sanchez A., Rech J., Labourdette D., Dorignac J., Geniet F., Palmeri J.,
Parmeggiani A., Boudsocq, Leberre V., Walter* J.-C. and Bouet* J.-Y Mol. Syst. Biol. 14, e8516 (2018).
[3] David G., Walter J.-C., Broedersz C., Dorignac J., Geniet F., Parmeggiani A., Walliser N.-O. and
Palmeri J., submitted to Phys. Rev. Lett. [arXiv/1811.09234] (2019).