Karlyshev, A. (2021) 'Campylobacter' genome reshuffling. In: World Microbe Forum; 21 - 24 Jun 2021, Held online. (Unpublished)

Abstract

Introduction: Some bacteria are known to undergo extensive random genetic exchanges and genome rearrangements, which represent significant challenges for their studies, identification and classification. One example is Campylobacter jejuni, undergoing a relatively high frequency of random genomic changes variations, with genetically and phenotypically different lineages of the same strain identified in different labs. In particular, an NCTC11168 strain, which was originally fully motile, became non motile after lab passages, but was then able to produce fully motile clonal isolates. While some of spontaneous genetic changes may involve single nucleotide bases of the homopolymeric tracts, more substantial intracellular genetic alterations can be detected within a pure cell culture. In natural environment, where more than one strain of the species may be present, natural competence of some Campylobacter strains may allow inter-strain genetic exchange, further contributing to genetic variation. In this study we describe the molecular mechanisms of intercellular genetic exchanges in Campylobacter bacteria. Methods: The strains were cocultured in a liquid medium followed by plating onto Columbia blood agar, incubation for two days at 37C, isolation of single colonies followed by PCR using strain-specific markers. Genome sequencing of the isolates was conducted using IonTorrent PGM (LifeTechnologies, Themo Fisher Scientific), followed by read mapping onto the genomes of the original strains by using CLC Genomics Workbench software. The derived complete genome sequences of the hybrid strains were compared with the genomes of the donor and recipient strains using Mauve program and other tools of comparative genomics. Results: The study allowed the identification of mosaic structures of genomes of the hybrid strains containing regions from both recipient and donor strains. The results suggest that acquisition of spontaneously released DNA of the donor strains in cocultures may lead to genome reshuffling. Conclusion: To our knowledge, this is the first study describing the phenomenon of hybrid strain formation not involving conjugative gene transfer. The phenomenon discovered will assist in better understanding of the lifestyle of Campylobacter jejuni, which is the most wide-spread bacterial enteric pathogen. In addition, the results have implications in bacterial classification and taxonomy.

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