nucleoid

GO:0009295 · Nucleoid · Subcellular region · Proposed

The non-membrane-bounded subcellular region in which a bacterial chromosome is compacted and organized with nucleoid-associated proteins while remaining dynamically coupled to transcription and replication. [DOI:10.1038/nrmicro2261]

Xrefs: uniprot.location:SL-0187 — Nucleoid

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
chromosomal DNA	Dna	part of				ESSENTIAL	The genome polymer whose compaction and spatial organization define the nucleoid. `DOI:10.1038/nrmicro2261` Dorman reviews chromosome organization in the bacterial nucleoid.
nucleoid-associated proteins	Protein	part of				CONDITIONAL	Bend, bridge, wrap, and constrain DNA and couple chromosome structure to gene expression. `DOI:10.1038/nrmicro2261` The review covers major NAP families and their regulatory roles.

Taxonomic distribution

NCBITaxon:2 Bacteria — UNIVERSAL: The chromosome occupies a nucleoid rather than a membrane-bounded nucleus. [DOI:10.1038/nrmicro2261]

Canonical examples

NCBITaxon:562 Escherichia coli — Best-characterized bacterial nucleoid and NAP system. [DOI:10.1038/nrmicro2261]

Functions

chromosome organization GO:0051276 — Compacts and spatially organizes the chromosome while preserving access to DNA.
- DOI:10.1038/nrmicro2261 Nucleoid architecture is integrated with gene expression.

Mechanism graphs

NAPs and supercoils compact DNA into an organized nucleoid (FUNCTION)

Nucleoid-associated proteins bind the bacterial chromosome and alter its local geometry by bending, wrapping, bridging, and constraining DNA. These local nucleoprotein states combine with plectonemic supercoils and topological domains to compact the chromosome into a dynamic nucleoid that still supports DNA replication and transcription.

Subject	Predicate	Object	Evidence
nucleoid-associated proteins	bind	chromosomal DNA	`DOI:10.1038/nrmicro2261` Dillon and Dorman 2010 review NAP binding across the bacterial chromosome.
nucleoid-associated proteins	bend and bridge	locally bent and bridged DNA	`DOI:10.1371/journal.pgen.1008456` Verma, Qian and Adhya 2019 review DNA bending, looping, bridging and wrapping by nucleoid-associated architectural proteins.
locally bent and bridged DNA	constrains	plectonemic supercoiled loops	`DOI:10.1371/journal.pgen.1008456` Verma, Qian and Adhya 2019 describe NAP constraint of negative supercoils as a route to chromosome topological organization.
chromosomal DNA	folds into	plectonemic supercoiled loops	`DOI:10.1371/journal.pgen.1008456` Verma, Qian and Adhya 2019 describe larger bacterial chromosome loops as plectonemic forms induced by supercoiling.
plectonemic supercoiled loops	compact into	nucleoid	`DOI:10.1371/journal.pgen.1008456` Verma, Qian and Adhya 2019 review hierarchical compaction of E. coli chromosomal DNA into spatial domains and the nucleoid.
nucleoid	organizes	chromosome organization	`DOI:10.1038/nrmicro2261` Dillon and Dorman 2010 review the dynamic coupling of bacterial nucleoid structure with gene expression.

Evidence

DOI:10.1038/nrmicro2261 Bacterial nucleoid-associated proteins, nucleoid structure and gene expression.
DOI:10.1371/journal.pgen.1008456 Verma, Qian and Adhya 2019 review multiscale Escherichia coli nucleoid architecture.

Curation history

2026-08-30T19:30:00Z codex · CREATED_RECORD — Added as a literature-backed foundational seed. Identity checked against the 2026-07-01 Gene Ontology release; requires human review.
2026-08-31T03:48:24Z uniprot_sl · ADD_UNIPROT_SL_XREF — Added uniprot.location:SL-0187 (Nucleoid); mapping read from the GO line of UniProt subcell.txt.
2026-08-31T06:12:34Z claude · SET_COMPONENT_ROLE — component_role became required (#77) so the constituent/machinery distinction is machine-readable rather than prose. Set per component; ASSOCIATED_MACHINERY only where the protein acts on the already-assembled structure.
2026-09-04T01:18:32Z codex · ADD_CAUSAL_GRAPH — Added a FUNCTION graph for NAP-mediated DNA binding, bending, bridging, supercoil constraint, and multiscale chromosomal compaction into the nucleoid, with additional evidence from Verma, Qian and Adhya 2019.

Source: data/structures/nucleoid/nucleoid.yaml