Cited by 170Evolution and Genetic DynamicsProbiotics and Fermented FoodsGenomics and Phylogenetic Studies

The DOI matches its Crossref record; 64 of the 64 references it cites were found in a registry or an index; none of the 34 sources its claims cite is checked for support yet.

Microbial domestication signatures of Lactococcus lactis can be reproduced by experimental evolution

Open access
Bachmann, Herwig, Starrenburg, Marjo J.C., Molenaar, Douwe, Kleerebezem, Michiel, van Hylckama Vlieg, Johan E.T.·2012·Genome Research

Abstract

Experimental evolution is a powerful approach to unravel how selective forces shape microbial genotypes and phenotypes. To this date, the available examples focus on the adaptation to conditions specific to the laboratory. The lactic acid bacterium Lactococcus lactis naturally occurs on plants and in dairy environments, and it is proposed that dairy strains originate from the plant niche. Here we investigate the adaptation of a L. lactis strain isolated from a plant to a dairy niche by propagating it for 1000 generations in milk. Two out of three independently evolved strains displayed significantly increased acidification rates and biomass yields in milk. Genome resequencing, revealed six, seven, and 28 mutations in the three strains, including point mutations in loci related to amino acid biosynthesis and transport and in the gene encoding MutL, which is involved in DNA mismatch repair. Two strains lost a conjugative transposon containing genes important in the plant niche but dispensable in milk. A plasmid carrying an extracellular protease was introduced by transformation. Although improving growth rate and growth yield significantly, the plasmid was rapidly lost. Comparative transcriptome and phenotypic analyses confirmed that major physiological changes associated with improved growth in milk relate to nitrogen metabolism and the loss or down-regulation of several pathways involved in the utilization of complex plant polymers. Reproducing the transition from the plant to the dairy niche through experimental evolution revealed several genome, transcriptome, and phenotype signatures that resemble those seen in strains isolated from either niche.

Overview

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TL;DR

Propagating the plant isolate *Lactococcus lactis* KF147 in milk for 1000 generations reproduced several genomic, transcriptomic, and phenotypic signatures of dairy domestication, including improved growth and mutations in nitrogen metabolism. Two of three independently evolved strains grew significantly better in milk, and one became a mutator via a *mutL* deletion.

Key findings

  • After 1000 generations, two of three adapted strains had significantly increased acidification and biomass yield in milk: maximum cell density was 2.0-fold higher for NZ5521 (p = 0.006), 2.8-fold for NZ5522 (p < 0.001), and 1.41-fold for NZ5523 (p = 0.31) versus KF147; relative fitness was 1.48, 1.1, and 1.21, respectively.
  • Genome resequencing found 21, 4, and 6 SNPs in NZ5521, NZ5522, and NZ5523, plus 7 and 2 INDELs in NZ5521 and NZ5522; NZ5522 and NZ5523 lost an identical 51.3-kb Tn6098-like conjugative transposon. NZ5521 had a *mutL* deletion and a ~10-fold higher mutation frequency (10.02 vs. 1.34 × 10⁻⁷ mutations/generation for KF147).
  • The protease plasmid pNZ521 improved growth but was rapidly lost; no protease-positive strains were detected after 1000 generations. Transcriptome analysis found 291 of 1850 genes differentially expressed (p < 0.001), with an oligopeptide ABC transporter operon upregulated in NZ5521/NZ5522 via identical *oppD*/*oppC* upstream deletions, and plant-polymer utilization pathways downregulated, converging toward dairy strain IL594.

Methods

  • Experimental evolution: *L. lactis* KF147, a mung-bean sprout isolate carrying pNZ521, was serially propagated in reconstituted skimmed milk in three parallel cultures (SP1–SP3) for 1000 generations (~16.6 generations per transfer; effective population size 1.66 × 10⁶). After 300 generations, protease-positive cells were selected and further propagated.
  • Phenotypic and genomic characterization: acidification, CFU, and competition fitness assays; Illumina whole-genome resequencing with PCR/amplicon validation; fluctuation analysis for mutation rates.
  • Transcriptome analysis: custom Agilent microarrays comparing adapted strains, KF147, KF147_PRT, and dairy isolate IL594 during exponential growth in milk, using 1850 genes covered by 100% matching probes.

Limitations

  • Stated: the 300-generation bottleneck (only ~100 protease-positive colonies per culture) may have lost beneficial mutations; *oppC* probe mismatch may underestimate IL594 expression; averaged P-values are not FDR-corrected; the authors cannot exclude that the GadR homolog regulates additional genes.
  • Evident: the study uses one plant isolate, three evolved lines, and one clone per line under laboratory milk conditions, so it does not directly demonstrate the natural plant-to-dairy transition.

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Integrity signals

Registry

Crossref · 10.1101/gr.121285.111

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Claims the paper makes

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  • It may state two separate claims as one. 30
  • Probably not a substantial claim. 19
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Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • OppC and oppD deletions are assigned inconsistently

    Major

    The text and Table 2 assign the adenine deletion 48 bases upstream to oppD and the thymidine deletion 64 bases upstream to oppC. Figure 3 reverses those assignments, attributing the thymidine deletion to oppD and the adenine deletion to oppC; this changes which mutation is proposed to explain increased expression.

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Research works printed but not linked: 1

  1. Sambrook J , Fritsch EF , Maniatis T . 1989. Molecular cloning: A laboratory manual, 2nd ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY.

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Metadata

Authors
Bachmann, H., Starrenburg, M. J. C., Molenaar, D., Kleerebezem, M., & van Hylckama Vlieg, J. E. T.
Affiliations
Nederlands Instituut Voor Zuivel Oonderzoek (NL)
Venue
Genome Research
Published
2011-11-11
Volume
22
Issue
1
Pages
115-124
ISSN
1088-9051 (ISSN-L)
OpenAlex
W2037362492
Cited by
170
References
63
Citations by year
2026: 6 · 2025: 9 · 2024: 12 · 2023: 7 · 2022: 12 · 2021: 15 · 2020: 9 · 2019: 17 · 2018: 10 · 2017: 13 · 2016: 10 · 2015: 16 · 2014: 14 · 2013: 11 · 2012: 8
Type
posted content
Language
en
Open access
Locations
  • Genome Research (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • VU Research Portal (publishedVersion)
  • Socio-Environmental Systems Modeling (acceptedVersion)
  • HighWire Press Open Archive (submittedVersion)
  • Data Archiving and Networked Services (DANS) (submittedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Evolution and Genetic Dynamics
  • Life Sciences › Agricultural and Biological Sciences › Food Science › Probiotics and Fermented Foods
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Phylogenetic Studies
Keywords
Lactococcus lactis, experimental evolution, niche adaptation, milk acidification, nitrogen metabolism, amino acid biosynthesis, genome resequencing, transcriptome, lactic acid bacteria
MeSH terms
Dairy Products, Lactococcus lactis, Transcription, Genetic, Gene Expression Regulation, Bacterial, Genome, Bacterial, Point Mutation, Evolution, Molecular, Genetic Loci

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