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See detailThe nucleotide excision repair (NER) system of Helicobacter pylori: Roles of NER components in mutation prevention and chromosomal import patterns after natural transformation
Moccia, Claudia; Kulick, Stefan; Krebes, Juliane et al

in BMC Microbiology (2012), 6(12), 67

Extensive genetic diversity and rapid allelic diversification are characteristics of the human gastric pathogen Helicobacter pylori, and are believed to contribute to its ability to cause chronic ... [more ▼]

Extensive genetic diversity and rapid allelic diversification are characteristics of the human gastric pathogen Helicobacter pylori, and are believed to contribute to its ability to cause chronic infections. Both a high mutation rate and frequent imports of short fragments of exogenous DNA during mixed infections play important roles in generating this allelic diversity. In this study, we used a genetic approach to investigate the roles of nucleotide excision repair (NER) pathway components in H. pylori mutation and recombination. [less ▲]

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See detailMicroevolution of Helicobacter pylori during prolonged infection of single hosts and within families.
Morelli, Giovanna; Didelot, Xavier; Kusecek, Barica et al

in PLoS genetics (2010), 6(7), 1001036

Our understanding of basic evolutionary processes in bacteria is still very limited. For example, multiple recent dating estimates are based on a universal inter-species molecular clock rate, but that ... [more ▼]

Our understanding of basic evolutionary processes in bacteria is still very limited. For example, multiple recent dating estimates are based on a universal inter-species molecular clock rate, but that rate was calibrated using estimates of geological dates that are no longer accepted. We therefore estimated the short-term rates of mutation and recombination in Helicobacter pylori by sequencing an average of 39,300 bp in 78 gene fragments from 97 isolates. These isolates included 34 pairs of sequential samples, which were sampled at intervals of 0.25 to 10.2 years. They also included single isolates from 29 individuals (average age: 45 years) from 10 families. The accumulation of sequence diversity increased with time of separation in a clock-like manner in the sequential isolates. We used Approximate Bayesian Computation to estimate the rates of mutation, recombination, mean length of recombination tracts, and average diversity in those tracts. The estimates indicate that the short-term mutation rate is 1.4 x 10(-6) (serial isolates) to 4.5 x 10(-6) (family isolates) per nucleotide per year and that three times as many substitutions are introduced by recombination as by mutation. The long-term mutation rate over millennia is 5-17-fold lower, partly due to the removal of non-synonymous mutations due to purifying selection. Comparisons with the recent literature show that short-term mutation rates vary dramatically in different bacterial species and can span a range of several orders of magnitude. [less ▲]

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