ParABS system induces topological modifications to spatio-temporally organize its mother and daughter chromosomes in the replicating C. crescentus cell

Shailesh Sathe; Apratim Chatterji

Home/Archive/arXiv

arXiv · 2610.03118

ParABS system induces topological modifications to spatio-temporally organize its mother and daughter chromosomes in the replicating C. crescentus cell

Shailesh Sathe·Apratim Chatterji

View original source ↗Read source document ↗Export metadata ↓

Abstract

We identify an entropy-mediated mechanism underlying the spatiotemporal organization of the chromosome in the bacterial cell Caulobacter crescentus. Effective entropic interactions between replicating DNA segments emerge from their topological modifications of daughter DNA polymers caused by transient ParA-ParB binding. Enthalpic contributions arising from the ParABS system further influence their dynamics. In C. crescentus, chromosome replication and segregation occur concurrently before cell division. The origin of replication oriC of the mother chromosome of C. crescentus is tethered to the old cell pole. Replication generates two daughter oriCs, one of which remains anchored at the old pole. The other oriC is actively transported toward the new pole by the ParABS system of proteins even as replication of the rest of the chain is in progress. How ParABS generates a directed force to transport a daughter oriC to the opposite pole during chromosome replication remains unclear. Furthermore, the two daughter chromosomes get neatly segregated into two halves of the cell. In a bead-spring polymer model of the replicating C. crescentus chromosome, we model transient ParA-ParB contacts that generate DNA loops and an effective entropic repulsion. This repulsion drives chromosome segregation and produces oriC trajectories consistent with experiments, aided by the ParA concentration gradient near the new pole. This minimal framework, incorporating the physics of topologically modified (ToMo) polymers, allows us to quantitatively reproduce the time-dependent spatial organization of different tagged loci and replisomes observed in multiple experiments. Incorporating a minimal model of extrusion also allows us to recover the linear arrangement of the chromosome arms, as is inferred from the characteristic diagonals of Hi-C maps.

Explore related subjects

cond-mat.soft

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Shailesh Sathe, Apratim Chatterji. 2026-10-02. ParABS system induces topological modifications to spatio-temporally organize its mother and daughter chromosomes in the replicating C. crescentus cell. https://arxiv.org/abs/2610.03118

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Inclined surfaces bias bacterial swarming expansion and edge organization

Bacterial swarming is the collective expansion of dense populations of motile cells across hydrated soft surfaces, yet gravity is usually treated as a fixed background condition in standard horizontal assays. We used surface inclination to examine how agar-surface orientation relative to gravity affects the expansion of Enterobacter sp. SM3 swarms. Colony expansion depended non-monotonically on inclination, with the strongest spreading at intermediate inclinations and weaker expansion under shallow or near-inverted conditions. Paired up-facing acute and down-facing obtuse configurations with the same tilt magnitude showed different expansion responses, suggesting that swarm expansion depended on both tilt magnitude and which side of the agar surface faced upward relative to gravity. Inclination also produced downhill-biased colony morphologies. PIV analysis showed generally lower mean activity under inclination than in the flat references, with a non-monotonic angular response and inward increases in speed and spatial velocity-correlation length. The downhill tip showed slower motion, shorter spatial correlations and smaller vortex cores than the upper region. To interpret the macroscopic trends, we extended a two-phase thin-film model by introducing an effective gravity coupling projected normal and tangential to the agar surface. Simulations suggest that the surface-tangential component mainly drives lateral redistribution, whereas the surface-normal component modifies film pressure and thereby pressure-dependent water replenishment, helping distinguish up-facing from down-facing configurations.

cond-mat.soft↗

arXiv2026

Activated coarsening of motility-induced phase separation in random environments

Self-propelled particles that only repel one another can still separate into a dense and a dilute phase, a process known as motility-induced phase separation (MIPS). In a clean system the domains coarsen like any conserved mixture: domains grow as $\ell(t)\sim t^{1/3}$. Living and synthetic swimmers, however, move through rough, porous, or patterned surroundings. Using large-scale simulations of active Brownian particles, we ask how frozen heterogeneity changes MIPS coarsening. We introduce disorder in two ways, as a quenched random force field acting on particle positions and as a quenched random torque field acting on their orientations. Both destroy Lifshitz-Slyozov growth. A transient power law with a disorder-dependent exponent gives way to activated dynamics in which the effective dynamic exponent grows without bound and domains grow at most logarithmically. The crossover obeys the scaling form known from the random-field Ising model, and the domain morphology depends on disorder strength, so superuniversality fails. The two kinds of disorder act through different mechanisms. Random forces trap particles in the sinks of a random drift field once the drift beats self-propulsion. Random torques act as a sign-random, quenched chirality that erodes persistence and lowers the local Péclet number toward its critical value. Our results show that quenched disorder is a relevant perturbation for the kinetics of active phase separation and connect MIPS coarsening to the physics of pinned interfaces in disordered magnets.

cond-mat.soft↗

arXiv2026

Compression-controlled dynamic buckling in thin soft sheets

We investigate experimentally the dynamic phase transition from compressed to buckled phases for thin sheets of rubber. We find that the rubber strips enter a highly compressed, metastable state when compression speed is high. During the compressed phase, higher modes grow, followed by mode coarsening. Mode growth is accompanied by an expansion of length while the system is still being compressed. We measure the forces and length of the sheet to confirm this, and we develop a mechanism for how modes grow and coarsen during dynamical buckling. The influence of crucial control parameters in the experiments, such as the material cross section and compression speed, on the buckling dynamics, are explained theoretically.

cond-mat.soft↗