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Updated: Jun 10, 2026
10:52
Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
Published on: August 13, 2016
A spindle-like apparatus guides bacterial chromosome segregation
Jerod L Ptacin1, Steven F Lee, Ethan C Garner
1Department of Developmental Biology, Stanford University School of Medicine, Beckman Center, Stanford, CA 94305, USA.
Nature Cell Biology
|July 27, 2010
Summary
Bacteria use a novel partitioning (Par) system for chromosome segregation, sharing principles with eukaryotic cell division. This bacterial spindle mechanism involves dynamic protein polymers and a Brownian ratchet for DNA movement.
Area of Science:
- Cell Biology
- Microbiology
- Genetics
Background:
- Chromosome segregation is essential for cell division.
- Eukaryotic cells utilize a complex mitotic apparatus (spindle) for chromosome segregation.
- Previously, such dedicated segregation machinery was thought to be exclusive to eukaryotes.
Purpose of the Study:
- To investigate the mechanism of chromosome segregation in the bacterium Caulobacter crescentus.
- To identify components and understand the dynamics of the bacterial partitioning (Par) system.
- To compare bacterial chromosome segregation with eukaryotic cell division.
Main Methods:
- In vitro polymerization assays for the ParA protein.
- In vivo imaging of ParA structures within Caulobacter crescentus.
- Biochemical analysis of ParB interaction with ParA polymers.
- Identification and characterization of the TipN protein's role.
Main Results:
- Caulobacter crescentus ParA forms linear polymers in vitro and in vivo.
- ParB binding destabilizes ParA polymers, driving centromere movement via a burnt bridge Brownian ratchet mechanism.
- The TipN protein is identified as a novel component essential for directional DNA segregation.
Conclusions:
- The bacterial Par system shares fundamental operating principles with eukaryotic mitotic machines.
- Dynamic polymer disassembly is a conserved mechanism for chromosome segregation.
- This study reveals a sophisticated bacterial chromosome segregation apparatus with parallels to eukaryotic spindles.
Related Concept Videos
02:27The Mitotic Spindle
The mitotic spindle—or spindle apparatus—is a eukaryotic, cytoskeletal structure made up of long protein fibers called microtubules. Formed during cell division, the spindle separates sister chromatids and moves them to opposite ends of a parental cell, where the now individual chromosomes are distributed to two daughter cell nuclei.
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...
02:27The Mitotic Spindle
The mitotic spindle—or spindle apparatus—is a eukaryotic, cytoskeletal structure made up of long protein fibers called microtubules. Formed during cell division, the spindle separates sister chromatids and moves them to opposite ends of a parental cell, where the now individual chromosomes are distributed to two daughter cell nuclei.
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...
02:50Spindle Assembly
Spindle assembly occurs through three, often coexisting, pathways – the centrosome-mediated pathway, the chromatin-mediated pathway, and the microtubule-mediated pathway – collectively contributing to form a robust spindle apparatus.
In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a microtubule array...
In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a microtubule array...
02:11Forces Acting on Chromosomes
During mitosis, chromosome movements occur through the interplay of multiple piconewton level forces. In prometaphase, these forces help in chromosome assembly or congression at the equatorial plane, eventually leading to their alignment at the metaphase plate. The forces acting on the chromosomes are space and time-dependent; therefore, they vary with the position of the chromosomes as the cell progresses through mitosis.
Microtubules and motor proteins exert two types of forces on...
Microtubules and motor proteins exert two types of forces on...
01:39Anaphase A and B
Microtubules form through the end-to-end polymerization of tubulin heterodimers. Kinetochore microtubules originate from the spindle poles, and their plus-ends connect with the kinetochores on sister-chromatids. Ndc80 protein complexes, present on the kinetochore, form low-affinity links with the plus end of these kinetochore microtubules.
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...
01:39Anaphase A and B
Microtubules form through the end-to-end polymerization of tubulin heterodimers. Kinetochore microtubules originate from the spindle poles, and their plus-ends connect with the kinetochores on sister-chromatids. Ndc80 protein complexes, present on the kinetochore, form low-affinity links with the plus end of these kinetochore microtubules.
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...