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Twelve populations of Escherichia coli B all lost D-ribose catabolic function during 2,000 generations of evolution in glucose minimal medium. We sought to identify the population genetic processes and molecular genetic events that caused these rapid and parallel losses. Seven independent Rbs(-) mutants were isolated, and their competitive fitnesses were(More)
Molecular methods are used widely to measure genetic diversity within populations and determine relationships among species. However, it is difficult to observe genomic evolution in action because these dynamics are too slow in most organisms. To overcome this limitation, we sampled genomes from populations of Escherichia coli evolving in the laboratory for(More)
Intrachromosomal homologous recombination in whole tobacco plants was analyzed using beta-glucuronidase as non-selectable marker. We found that recombination frequencies were additive for transgenes in allelic positions and could be enhanced by treatment of plants with DNA-damaging agents. We compared the patterns of distribution of recombination events of(More)
BACKGROUND Insertion Sequence (IS) elements are mobile genetic elements widely distributed among bacteria. Their activities cause mutations, promoting genetic diversity and sometimes adaptation. Previous studies have examined their copy number and distribution in Escherichia coli K-12 and natural isolates. Here, we map most of the IS elements in E. coli B(More)
A transposable element (TE) is a mobile sequence present in the genome of an organism. TEs can cause lethal mutations by inserting into essential genes, promoting deletions or leaving short sequences upon excision. They therefore may be gradually eliminated from mixed populations of haploid micro-organisms such as Escherichia coli if they cannot balance(More)
Bacterial subclones recovered from an old stab culture of Escherichia coli K-12 revealed a high degree of genetic diversity, which occurred in spite of a very reduced rate of propagation during storage. This conclusion is based on a pronounced restriction fragment length polymorphism (RFLP) detected upon hybridization with internal fragments of eight(More)
An analysis of restriction fragment length polymorphism (RFLP) using eight residential insertion sequence (IS) elements as hybridization probes reveals that the genome of resting bacteria is more dynamic than it was long believed. Escherichia coli strains stored in agar stabs for up to 30 yr accumulate a genetic variation which is correlated to time of(More)
As part of a long-term evolution experiment, two populations of Escherichia coli B adapted to a glucose minimal medium for 10,000 generations. In both populations, multiple IS-associated mutations arose that then went to fixation. We identify the affected genetic loci and characterize the molecular events that produced nine of these mutations. All nine were(More)
The loss of preexisting genes or gene activities during evolution is a major mechanism of ecological specialization. Evolutionary processes that can account for gene loss or inactivation have so far been restricted to one of two mechanisms: direct selection for the loss of gene activities that are disadvantageous under the conditions of selection (i.e.,(More)
The bleomycin resistance gene (ble) of transposon Tn5 is known to decrease the death rate of Escherichia coli during stationary phase. Bleomycin is a DNA-damaging agent and bleomycin resistance is produced by improved DNA repair which also requires the host genes aidC and polA coding, respectively, for an alkylation-inducible gene product and DNA polymerase(More)