Generation of Campylobacter jejuni genetic diversity in vivo

Abstract

SummaryMolecular epidemiology studies suggest that horizontal genetic exchange is a major cause of pathogen biodiversity. We tested this concept for the bacterial enteropathogen Campylobacter jejuni by seeking direct in vivo evidence for the exchange of genetic material among Campylobacter strains. For this purpose, two antibiotic resistance markers were inserted into the hipO or htrA gene of genetically distinct and naturally transformable C. jejuni strains. Genetic exchange of the resistance markers was analysed after co-cultivation of homologous and heterologous strains in vitro and in vivo during experimental infection of chickens. Double-resistant recombinants were obtained both in vitro and from the chicken intestine for all combinations of strains tested. Bidirectional genetic exchange of DNA between homologous and heterologous strains was confirmed by Southern blotting in combination with flaA polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), amplified fragment length polymorphism (AFLP) and pulsed field gel electrophoresis (PFGE). Extensive PFGE analyses of isolated recombinants indicated the frequent occurrence of genetic rearrangements during the experimental infection, in addition to the homologous recombination of the antibiotic resistance genes. Together, the data indicate unequivocally that interstrain genetic exchange as well as intragenomic alterations do occur in vivo during C. jejuni infection. These events probably explain the genome plasticity observed for this pathogen.

A Genomic Island Defines Subspecies-Specific Virulence Features of the Host-Adapted Pathogen Campylobacter fetus subsp. venerealis

“…Additionally, genetic diversity may be limited by the lack of natural competence in C. fetus (77). Other campylobacters, like C. jejuni or H. pylori, show extensive genetic variation, vertically as well as horizontally, and these continuous genetic alterations are important traits of the pathogens for colonizing and persisting in their habitats (10,18,85).…”

Genetic Characterization and Antibiotic Resistance of Campylobacter jejuni Isolated from Meats, Water, and Humans in Sweden

“…There are also indications that C. jejuni can undergo intensive recombination leading to different PFGE patterns. However, this phenomenon seems to occur at low frequencies and under certain unknown conditions (3,28).…”

Change Is Good: Variations in Common Biological Mechanisms in the Epsilonproteobacterial GeneraCampylobacterandHelicobacter

“…Both C. jejuni and H. pylori display enormous amounts of genetic diversity (171,580,643). Furthermore, maintaining inter-and intrastrain diversity has been shown to provide a fitness advantage in vivo (43,125,279,307,643). Because of this fact, the ability to acquire new genes or alleles is of the utmost importance.…”

“…Thus, acquisition of exogenous DNA results in genetic diversity within a population of bacteria and provides the necessary framework for genomic evolution. As a result, this diversity often provides an in vivo fitness advantage for pathogenic bacteria (43,125,307,580). Natural transformation is a multistep process that can be divided into the following steps: binding of DNA to the bacterial surface, transport of DNA across the bacterial membrane(s) into the cytoplasm, and integration of nonplasmid donor DNA into the recipient chromosome by homologous recombination.…”