Part of the cell · Cell division and structural integrity
Dividing into two cells
On the cell picture: Cell division
Holding the cell's shape and pinching it into two viable daughters at the right place and the right moment.
Proteins in the model: 55
Part of the model's 1051 proteins. Each group below is a book group, counted in the working count after the repeats and non-first-cell groups were removed. The proteins are not yet matched gene by gene.
| Group | Proteins |
|---|---|
| Membrane maintenance | 4 |
| General secretion | 11 |
| Acidocalcisome components | 4 |
| HGT mechanisms | 10 |
| Protein secretion systems | 5 |
| Protein export machinery | 5 |
| Cell division proteins | 4 |
| Min system proteins | 4 |
| DNA management proteins | 3 |
| Regulation and timing | 5 |
Its pathways
- Peptidoglycan precursorsatlas pathway9
- Wall synthesis and remodelingatlas pathway7
- Division scaffoldatlas pathway3
- Envelope assembly and divisionatlas pathway2
- Division-associated membrane partsatlas pathway1
- Peptidoglycan biosynthesisKEGG map3
- Not yet placed in a pathwayto sort19
If it fails
Metabolism carries on, but the cell either grows into a filament or bursts. No offspring are produced.
Cannot divide · at the next division
What it depends on
- Building and maintaining the membraneDaughter-cell formation requires expansion and partitioning of the cell envelope.Book pp. 500–501, 504
- Copying and repairing the genomeChromosome replication and segregation must be coordinated with cellular partitioning.Book pp. 501, 504
- Reading genes into RNA, Building proteins and folding themTranslation provides structural and division proteins.Book pp. 501–502, 504
What it supplies
None listed in the curated set.
Dependencies are curated from the book at the level of the map’s systems and are not measured protein contacts. See all systems together.
How it is built and controlled
Counts from UniProt annotations of this group’s proteins.
Its place in the control layer
None of this group’s proteins appear in the information, signaling, regulation, machine-signal or assembly lists.
From the control-layer pages. Which genes a regulator controls is mostly inferred from related bacteria, because Aquifex has no genetic system for testing it directly.
Origins
What needs to be explained
How did growth, compartment division and inheritance become coordinated in early reproducing systems?
What needs explaining. Explain growth, genome inheritance and physical separation that yield viable descendants, while allowing that early division could differ from modern divisomes.
Hurdles
- H-DIV-1Coordinated growthThe problem. To split into two cells of equal size, the surface must grow by about 26% more than the volume alone would require.Why it is hard. Membrane and contents grow by different processes; if they are not matched, cells swell, shrink or divide unevenly.The integrated cellStage 2: One step shown on its ownShown: Fatty-acid vesicles grow by taking up new amphiphiles.In the books: 64 open problems on cell division and structure ↗
- H-DIV-2Content retentionThe problem. Division must separate the membrane into two closed compartments without losing contents.Why it is hard. Cells constrict and seal the membrane with a ring of FtsZ and partner proteins; without such a machine, division tears or leaks.Molecular machinesStage 2: One step shown on its ownShown: Vesicles can divide while keeping most of their contents (Zhu & Szostak 2009).In the books: 64 open problems on cell division and structure ↗
- H-DIV-3Genome partitioningThe problem. Each daughter must receive at least one complete genome.Why it is hard. With only one or a few genome copies, random splitting leaves some daughters without genes; cells prevent this with active partitioning systems.Information and controlStage 0: Not yet addressed by experimentShown: not yet addressed by experiment.In the books: 64 open problems on cell division and structure ↗
- H-DIV-4Reproductive continuityThe problem. Each daughter must contain enough of every essential component (ribosomes, enzymes, membrane) to start growing again.Why it is hard. Missing even one essential component in a daughter ends that line.The integrated cellStage 3: Several steps shown working togetherShown: Growth and division repeat over several cycles in the laboratory, without an internal metabolism.In the books: 64 open problems on cell division and structure ↗
- H-DIV-5Coordinated timingThe problem. Division must wait until the genome has been copied and separated, and growth must keep pace with both.Why it is hard. Cells time these events with dedicated regulators (DnaA, FtsZ and nucleoid occlusion). Without timing, daughters are empty or overfilled.Information and controlStage 2: One step shown on its ownShown: Vesicles carrying RNA can take membrane from empty ones (Chen et al. 2004), a physical link between contents and growth; timing growth, copying and division together has not been shown.In the books: 64 open problems on cell division and structure ↗
Scope. How a modern bacterium divides and how a first compartment could divide without proteins are separate questions. An origins explanation must connect these stages rather than equate them.
Experimental progress. Gene-addition experiments in engineered minimal cells identify contributors to division and morphology. These cells depend on provided culture conditions and are not a reconstructed prebiotic cell.
What would strengthen a natural account. Steps shown to work together under plausible early-Earth conditions, without a chemist choosing the reagents, purifying the products or changing conditions between steps, would strengthen a natural account of origins in proportion to what they explain. Loss of a claimed dependency or discovery of functional alternatives would weaken the corresponding design argument. Gaps in the record do not supply a numerical likelihood for either explanation.
Observations. Division components must assemble at an appropriate location and geometry. Chromosome handling and physical division contribute different requirements for viable descendants.
Hallmarks that apply.
- H28 Co-location of components: Division components must assemble at an appropriate location and geometry.
- H31 Self-replication with fidelity: Chromosome handling and physical division contribute different requirements for viable descendants.
- H40 Cross-domain constraint satisfaction: DNA inheritance, envelope growth and division must be coordinated.
The author’s conclusion. The coordinated features give the author a positive reason to consider design within the wider cellular architecture. For this local system alone, they do not establish that design is uniquely the best historical explanation. The conservative inference is that the system contributes to a cumulative design case, with its weight conditional on the comparative evidence and on how much plausible natural pathways explain.
From the book article Cell Division and Structure, with its scientific references.
How it was discovered
- 1989De Boer, Crossley and Rothfield describe the Min system, which keeps division at the middle of the cell.de Boer, Crossley & Rothfield, Cell 56:641–649 (1989)
- 1991Bi and Lutkenhaus see FtsZ form a ring at the site where the cell will divide.Bi & Lutkenhaus, Nature 354:161–164 (1991)
- 1998Löwe and Amos solve the structure of FtsZ and find it resembles tubulin.Löwe & Amos, Nature 391:203–206 (1998)
- 2004Vesicles carrying RNA are shown to grow by taking membrane from empty neighbours.Chen, Roberts & Szostak, Science 305:1474–1476 (2004)
- 2009Bacteria without a cell wall (L-forms) are shown to divide without FtsZ.Leaver et al., Nature 457:849–853 (2009)
- 2021Adding back a few genes restores regular division in the minimal cell JCVI-syn3A.Pelletier et al., Cell 184:2430–2440 (2021)
Each hurdle above is sorted by kind and by how far experiments have got (see “How hurdles are sorted” at the top).
All parts of the cell side by side: origins hub. The book articles:
- Cell Division and Structure: system page · full description · origins