Insertion-sequence-mediated mutations isolated during adaptation to growth and starvation in Lactococcus lactis

We studied the activity of three multicopy insertion sequence (IS) elements in 12 populations of Lactococcus lactis IL1403 that evolved in the laboratory for 1000 generations under various environmental conditions (growth or starvation and shaken or stationary). Using RFLP analysis of single-clone r...

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Bibliographic Details
Published in:Genetics (Austin) 2004-11, Vol.168 (3), p.1145-1157
Main Authors: Visser, J.A.G.M. de, Akkermans, A.D.L, Hoekstra, R.F, Vos, W.M. de
Format: Article
Language:English
Subjects:
Adaptation, Physiological - genetics
adaptive evolution
Bacteria
beneficial mutations
Culture Techniques
diversity
DNA Transposable Elements
Environmental conditions
escherichia-coli
generations
Investigations
Lactococcus lactis
Lactococcus lactis - genetics
Lactococcus lactis - physiology
Molecular Probes
Mutation
Polymorphism, Restriction Fragment Length
Population genetics
populations
rearrangements
Sequence Deletion
stationary-phase
Studies
term experimental evolution
transposable elements
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Summary:We studied the activity of three multicopy insertion sequence (IS) elements in 12 populations of Lactococcus lactis IL1403 that evolved in the laboratory for 1000 generations under various environmental conditions (growth or starvation and shaken or stationary). Using RFLP analysis of single-clone representatives of each population, nine IS-mediated mutations were detected across all environmental conditions and all involving IS981. When it was assumed that these mutations were neutral, their frequency was higher under shaken than under stationary conditions, possibly due to oxygen stress. We characterized seven of the nine mutations at the molecular level and studied their population dynamics where possible. Two were simple insertions into new positions and the other five were recombinational deletions (of 10 kb) among existing and new copies of IS981; in all but one case these mutations disrupted gene functions. The best candidate beneficial mutations were two deletions of which similar versions were detected in two populations each. One of these two parallel deletions, affecting a gene involved in bacteriophage resistance, showed intermediate rearrangements and may also have resulted from increased local transposition rates.
ISSN:0016-6731
1943-2631
1943-2631
DOI:10.1534/genetics.104.032136