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Abstract The mechanisms by which two sister chromosomes separate and partition into daughter cells in bacteria remain poorly understood. A recent theoretical model has proposed that out-of-equilibrium processes associated with mRNA–ribosome (polysome) dynamics play a significant role in this process. Here we investigate the role of ribosomal dynamics on nucleoid segregation and separation inEscherichia coliusing high-throughput fluorescence microscopy in microfluidic devices. We compare our experimental observations with predictions from a reaction-diffusion model that includes the interactions among ribosomal subunits, polysomes, and chromosomal DNA. Our results show that the non-equilibrium behavior of mRNA and ribosomes causes them to aggregate at the midcell and this process contributes to the separation of the two daughter chromosomes. However, this effect is considerably weaker than that predicted by the model. Rather than relying solely on active mRNA–ribosome dynamics, our data suggest that the closing division septum via steric interactions and potentially entropic forces between two DNA strands coupled to cell elongation act as additional mechanisms to ensure faithful partitioning of the nucleoids to two daughter cells. SignificanceThe mitotic spindle separates chromosomes in eukaryotic cells, but bacteria lack this structure. It remains unclear how bacterial chromosomes partition prior to cell division. It has been hypothesized that non-equilibrium dynamics of polysomes, that is mRNA–ribosome complexes, actively drive the separation of bacterial chromosomes. Using quantitative microscopy combined with computational modeling, we show that polysome dynamics significantly contribute to chromosome segregation inEscherichia colibut this process does not constitute the sole mechanism. Our findings suggest the closing division septum via steric interactions and potentially entropic forces between two DNA strands act as additional mechanisms.
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This content will become publicly available on November 11, 2026
The role of active mRNA–ribosome dynamics and closing constriction in daughter chromosome separation in Escherichia coli
The mechanisms by which two sister chromosomes separate and partition into daughter cells in bacteria remain poorly understood. A recent theoretical model has proposed that out-of-equilibrium central dogma reactions involving mRNA and ribosomes play a significant role in this process. Here, we test this idea in theEscherichia colimodel system using high-throughput fluorescence microscopy in microfluidic devices. We compare our experimental observations with predictions from a reaction–diffusion model that includes central dogma-related reactions and excluded volume interactions between ribosomal subunits, polysomes, and chromosomal DNA. Our results show that the nonequilibrium reactions of ribosomes cause them to aggregate at the midcell, and this process facilitates the separation of the two daughter chromosomes. However, the observed effects are weaker in live cells than our one-dimensional reaction–diffusion model predicts. Rather than relying solely on active mRNA–ribosome dynamics, our data suggest that the closing division septum via steric interactions and potentially entropic forces between two DNA strands coupled to cell elongation act as additional mechanisms to ensure faithful partitioning of the nucleoids to two daughter cells.
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- Award ID(s):
- 2313719
- PAR ID:
- 10684333
- Publisher / Repository:
- National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 122
- Issue:
- 45
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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