<i>C. coli</i>/<i>C. jejuni</i> hybrids - extended natural interspecies transformation

Campylobacter is the leading food-borne pathogen in Europe, although the bacterium is considered highly stress-sensitive. Indeed it displays fastidious needs for growth in vitro and for survival in the environment. However, the bacterium exhibits high genetic diversity and, therefore, adapts to changing conditions, leading to the persistence throughout the food chain. However, the underlying mechanisms are largely unknown but of high interest for food safety.Here, we identified strains with huge interspecies genetic exchange, which might be a result to adaptation to a harsh environment. These strains, for which species typing with classical PCR methods was impaired, also did not yield satisfactory results using MLST typing due to high natural transformation activity. According to cgMLST the strains were phylogenetically non-related. An in-depth k-mer analysis of whole genome sequence data revealed extended incorporation of C. jejuni sequences in a common subset of genes in these C. coli strains, which might be indicative for adaptation to oxidative, osmotic and general stresses during persistence of these strains in food matrices, in par-ticular, on egg shells.Our results have practical impact for routine labs on the evaluation of classical typing methods and on the understanding of spreading and persistence of Campylobacter due to extended adaptive potential.