High frequency of hotspot mutations in core genes of Escherichia coli due to short-term positive selection.

摘要: Core genes comprising the ubiquitous backbone of bacterial genomes are not subject to frequent horizontal transfer and generally thought contribute adaptive evolution pathogens. We determined, however, that at least one-third possibly more than one-half core in Escherichia coli targeted by repeated replacement substitutions same amino acid positions—hotspot mutations. Occurrence hotspot mutations is driven positive selection, as their rate significantly higher expected random chance alone, neither intragenic recombination nor increased mutability can explain observed patterns. Also, commensal E. strains have a lower frequency mutated per genome pathogenic strains. causing extra-intestinal infections accumulate highest rate, whereas total number has been found among Shigella isolates, suggesting pathoadaptive nature such The vast majority recent evolutionary origin, implying short-term where emerge repeatedly but sustained natural circulation for long. Such pattern dynamics consistent with source-sink model virulence evolution.