409: A systems-level atlas of carbon-response transcriptional states in Escherichia coli

Shin J et al., PNAS - This episode examines a large transcriptome compendium (PRECISE-NP881) that profiles E. coli K-12 MG1655 across 43 carbon substrates. Independent component analysis resolved 137 iModulons, including 25 carbon-catabolism modules that organize substrates into four activity-defined groups tied to growth rate, substrate chemistry, metabolic entry routes, and proteome allocation. The study integrates growth phenotyping, FBA/ME-modeling, targeted knockouts, and reanalysis of a starvation/refeeding time course to connect transcriptional modules to physiological context. Key terms: carbon response, iModulon, Escherichia coli, carbon catabolite repression, transcriptional regulatory network.

Study Highlights:
The authors assembled PRECISE-NP881 (881 transcriptomes) and used ICA to define 137 iModulons, 25 of which are carbon-catabolism modules whose activities cluster substrates into four groups. Faster-growing sugars showed limited CRP-linked remodeling while slower-growth, non-glycolytic substrates activated CRP-linked, NtrC-1, Propionate, and SgcABCEQX iModulons. Targeted knockouts (e.g., ΔprpC) demonstrated conditional growth defects on Group C/D substrates supporting a role for methylcitrate-mediated propionyl-CoA processing. Proteome-allocation modeling and projection of an independent starvation/refeeding dataset corroborated links between carbon-response modules, growth/stress physiology, and metabolite dynamics.

Conclusion:
The paper provides a quantitative atlas of carbon-responsive transcriptional states in E. coli, decomposing CCR into separable CRP-linked and substrate-specific modules and linking these modules to growth rate, metabolic context, proteome allocation, and conditional physiological relevance.

Music:
Enjoy the music based on this article at the end of the episode.

Article title:
A systems-level atlas of carbon-response transcriptional states in Escherichia coli

First author:
Shin J

Journal:
PNAS

DOI:
10.1073/pnas.2531884123

Reference:
Shin J, Son HF, Krishnan J, Hefner Y, Szubin R, Sung J, Patel A, Lou XA, Catoiu EA, Palsson BØ, Zielinski DC. A systems-level atlas of carbon-response transcriptional states in Escherichia coli. PNAS. 2026;123(27):e2531884123. doi:10.1073/pnas.2531884123.

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/

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Episode link: https://basebybase.com/episodes/atlas-carbon-response-transcriptional-states-e-coli

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-07.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections describing PRECISE-NP881 atlas construction ( ICA/iModulons ), four substrate groups (A–D), CRP decomposition into Crp-1/Crp-2/Crp-3, NtrC-1 and Propionate iModulons linked to propionyl-CoA stress, methylcitrate pathway (prpC/astC), SgcABCEQX prophage iModulon, starvation/refeeding dynam
- transcript topics: ICA-based iModulon analysis; CRP-linked iModulons decomposition (Crp-1, Crp-2, Crp-3); Four substrate groups (A–D) and growth phenotypes; NtrC-1 and Propionate iModulons and propionyl-CoA stress; Methylcitrate pathway and prpC/astC functional evidence; SgcABCEQX prophage iModulon

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 6
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- 25 carbon-catabolism iModulons identified (out of 137 total iModulons)
- four activity-defined substrate groups (A–D) with distinct growth and metabolic patterns
- CRP network decomposes into Crp-1, Crp-2, Crp-3 iModulons
- NtrC-1 and Propionate iModulons associated with Group C/D substrates and methylcitrate pathway
- prpC (methylcitrate synthase) deletion reduces growth on Group C/D substrates but not on glucose
- SgcABCEQX prophage iModulon induced under nitrogen-containing, slower-growth conditions; not required for growth in tested conditions

QC result: Pass.