Browsing by Author "Yang, Xiaochang"

Campylobacter jejuni is one of the leading causes of human gastroenteritis. Globally, there has been an increasing trend in the incidence of campylobacteriosis. In the European Union, about 200,000 cases of campylobacteriosis are reported annually. C. jejuni 4031 was isolated from a water outbreak in Finland. This strain belongs to the ST-45 clonal complex. According to a previous study, this population has been stable over time and space and has showed low levels of genomic diversity compared with other populations. Therefore, it is meaningful to investigate the evolutionary mechanisms and ecological conditions behind these clones. The aim of this study was to investigate the evolution of C. jejuni 4031 by whole genome sequencing and bioinformatics tools, characterizing the rate and molecular spectrum of spontaneous mutation in these clones. In addition, the transformation pattern of C. jejuni 4031 was to be studied. This study composed of three independent experiments: mutation accumulation experiment, fluctuation analysis, and transformation cycle experiment, to investigate mutation and recombination events, respectively. The C. jejuni 4031 grown for 220 generations by single colony passaging method in NB2 agar plate and thereafter named C. jejuni 4031x12 was used as starting material for the studies. In total of 76 genomes from both mutation accumulation experiments and transformation cycle experiments, were subject to SNP calling. Results showed that C. jejuni 4031x12 could accumulate spontaneous mutations at a relatively low rate (4.1x10-10 mutation per generation per nucleotide) than conventional estimates, with mutational bias towards G:C>A:T transitions and coding regions. The fluctuation analysis proves that C. jejuni 4031x12 could obtain antibiotic resistance via transformation. However, no recombination events were observed from SNP results. In conclusion, C. jejuni 4031 has evolved at a much lower rate compared with prior knowledge. Results from fluctuation analysis and transformation cycle experiment suggest that there are no essential recombination barriers between C. jejuni 4031 and C. jejuni NCTC11168 but transformants may not have a competitive advantage over their non-transformed counterparts.