Laboratory-based evolution experiments on microorganisms that do not recombine frequently show two distinct phases: an initial rapid increase in fitness followed by a slower regime. To explore the population structure and the evolutionary tree in the later stages of adaptation, we evolved a very large population (∼3×1010) of Acinetobacter baylyi bacteria for approximately 2,800 generations from a single clone. The population was maintained in a chemostat at a high dilution rate. Nitrate in limiting amount and as the sole nitrogen source was used as a selection pressure. Analysis via resequencing of genomes extracted from populations at different generations provides evidence that long-term diversity can be established in the chemostat in a very simple medium. To find out which biological parameters were targeted by adaptation, we measured the maximum growth rate, the nitrate uptake, and the resistance to starvation. Overall, we find that maximum growth rate could be a reasonably good proxy for fitness. The late slow adaptation is compatible with selection coefficients spanning a typical range of 10-3-10 -2 per generation as estimated by resequencing, pointing to a possible subpopulations structuring.

Long-term diversity and genome adaptation of Acinetobacter baylyi in a minimal-medium chemostat / N. Jezequel, M. Cosentino Lagomarsino, F. Heslot, P. Thomen. - In: GENOME BIOLOGY AND EVOLUTION. - ISSN 1759-6653. - 5:1(2013), pp. 87-97. [10.1093/gbe/evs120]

Long-term diversity and genome adaptation of Acinetobacter baylyi in a minimal-medium chemostat

M. Cosentino Lagomarsino;
2013

Abstract

Laboratory-based evolution experiments on microorganisms that do not recombine frequently show two distinct phases: an initial rapid increase in fitness followed by a slower regime. To explore the population structure and the evolutionary tree in the later stages of adaptation, we evolved a very large population (∼3×1010) of Acinetobacter baylyi bacteria for approximately 2,800 generations from a single clone. The population was maintained in a chemostat at a high dilution rate. Nitrate in limiting amount and as the sole nitrogen source was used as a selection pressure. Analysis via resequencing of genomes extracted from populations at different generations provides evidence that long-term diversity can be established in the chemostat in a very simple medium. To find out which biological parameters were targeted by adaptation, we measured the maximum growth rate, the nitrate uptake, and the resistance to starvation. Overall, we find that maximum growth rate could be a reasonably good proxy for fitness. The late slow adaptation is compatible with selection coefficients spanning a typical range of 10-3-10 -2 per generation as estimated by resequencing, pointing to a possible subpopulations structuring.
Actinobacteria, genetics, physiology; Adaptation, Physiological, genetics; Cell Proliferation; Culture Media; Evolution, Molecular; Genetic Fitness; Genetic Variation; Genome, Bacterial; Microbiological Techniques; Nitrates, metabolism
Settore BIO/18 - Genetica
Settore FIS/01 - Fisica Sperimentale
Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici
GENOME BIOLOGY AND EVOLUTION
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/657978
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