Cited by 207CRISPR and Genetic EngineeringBacterial Genetics and BiotechnologyBiochemical and Structural Characterization

The DOI matches its Crossref record; 38 of the 39 references it cites were found in a registry or an index; none of the 47 sources its claims cite is checked for support yet.

The discovery of CRISPR in archaea and bacteria

Open access
Mojica, Francisco J. M., Rodriguez‐Valera, Francisco·2016·The FEBS Journal

Abstract

CRISPR-Cas are self-/nonself-discriminating systems found in prokaryotic cells. They represent a remarkable example of molecular memory that is hereditarily transmitted. Their discovery can be considered as one of the first fruits of the systematic exploration of prokaryotic genomes. Although this genomic feature was serendipitously discovered in molecular biology studies, it was the availability of multiple complete genomes that shed light about their role as a genetic immune system. Here we tell the story of how this discovery originated and was slowly and painstakingly advanced to the point of understating the biological role of what initially was just an odd genomic feature.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This is a historical account by Mojica and Rodríguez-Valera of how CRISPR was discovered in archaea and bacteria, beginning with an unexpected 30-bp repeat pattern in *Haloferax mediterranei* in 1992. It traces how exploratory prokaryotic genomics and spacer-matching analyses led to the recognition of CRISPR-Cas as an adaptive immune system.

Key findings

  • The first CRISPR-like repeats were found serendipitously in *Haloferax mediterranei*: DNA segments 30 bp long repeated at regular distances, with at least 14 almost perfectly conserved repeats flanked at one end by a highly degenerated copy.
  • Similar arrays were already known in bacteria: *E. coli* K12 had two DNA segments with 14 and 7 copies of a 29-bp sequence, and *Mycobacterium bovis* BCG had an array with 49 copies of a 36-bp direct repeat separated by 35–41 bp spacers.
  • By the end of the century, regularly spaced repeats had been discovered in 12 species of archaea and bacteria, with open access to 26 completed microbial genomes; a comprehensive study showed wide distribution and hinted at ancestral origin and high biological relevance.
  • Spacer analysis in *E. coli* showed that about 2% of spacers from 61 additional strains matched sequences in non-CRISPR loci, invariably in genetic elements of the corresponding spacer-carrier species, supporting CRISPR as an immunity system against foreign DNA.

Methods

  • Historical narrative/perspective article, not a primary experimental study; it recounts the authors’ discovery process and the field’s development.
  • Sources include the authors’ recollections, an unpublished Sanger sequencing gel dated 21/08/1992, an unpublished doctoral thesis, and published literature on CRISPR and prokaryotic genomes.
  • Main analysis is chronological and descriptive, linking early repeat observations, genome sequencing advances, spacer database searches, and later experimental demonstrations by other groups.

Limitations

  • Not stated in the paper: the article does not include a formal limitations section.
  • Evident from the text: it is a retrospective personal account, so it may be shaped by recall and perspective rather than systematic review.
  • Evident from the text: some reported experiments are unpublished results, and the authors describe publication rejections and lack of solid experimental evidence at the time, which limits the strength of the early immunity claims.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1111/febs.13766

Cites

38 of 38 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 47 cited sources checked · 0 supported · 0 flagged

Show all 33 claims

  • It may state two separate claims as one. 15
  • Probably not a substantial claim. 8
22 of 22
  • The paper relies on this without support.

    The four selected microorganisms (E. coli, Streptococcus pyogenes, Sulfolobus, and Methanothermobacter thermoautotrophicum) are representative of their respective prokaryotic groups such that common observations about their CRISPR loci apply to prokaryotes in general.

    “Four microorganisms were selected, as representatives of their respective prokaryotic groups, for further analysis: E. coli (Gram-negative bacteria), Streptococcus pyogenes (Gram-positive bacteria), Sulfolobus (crenarchaea) and Methanothermobacter thermoautotrophicum (euryarchaea).”
    “Hence, common observations related to their CRISPR loci would provide conclusions applying to the prokaryotes in general.”
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Cited works that were retracted

Works this paper cites that were later retracted, from the retraction notices publishers deposit. Major when the notice came out before this paper was published.

  • Cites a retracted work: 10.1038/nbt.3547

    Info

    The cited work was retracted on 2017-07-26 (notice 10.1038/nbt0817-797a), not before this paper was published (2016-06-15).

    Cited work 10.1038/nbt.3547 · retracted 2017-07-26 · notice 10.1038/nbt0817-797a · this paper published 2016-06-15

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Citations

Cites

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Metadata

Authors
Mojica, F. J. M., & Rodriguez‐Valera, F.
Affiliations
  • University of Alicante (ES)
  • Evolutionary Genomics Group Universidad Miguel Hernandez Alicante Spain
Corresponding author
Mojica, Francisco J. M.
Venue
The FEBS Journal
Publisher
Wiley
Published
2016-06-15
Volume
283
Issue
17
Pages
3162-3169
ISSN
  • 1742-464X (ISSN-L)
  • 1742-4658
OpenAlex
W2397372517
Cited by
207
References
39
Citations by year
2026: 10 · 2025: 24 · 2024: 27 · 2023: 22 · 2022: 36 · 2021: 26 · 2020: 19 · 2019: 11 · 2018: 18 · 2017: 11 · 2016: 3
FWCI
1.24
Type
journal article
Language
en
Open access
Locations
  • FEBS Journal (publishedVersion, other-oa)
  • PubMed (publishedVersion)
  • LA Referencia (Red Federada de Repositorios Institucionales de Publicaciones Científicas) (submittedVersion)
  • Repositorio Institucional de la Universidad de Alicante (Universidad de Alicante) (submittedVersion)
Funders
  • European Commission (291815)
  • Seventh Framework Programme
  • Generalitat Valenciana
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › CRISPR and Genetic Engineering
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Bacterial Genetics and Biotechnology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Biochemical and Structural Characterization
Keywords
CRISPR-Cas, archaea, bacteria, self/non-self discrimination, molecular memory, adaptive immunity
MeSH terms
Archaea, Bacteria, Genome, Bacterial, Genome, Archaeal, Genomics, CRISPR-Cas Systems

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