Project description:Although the majority of previous work on campylobacteriosis has centered on the species Campylobacter jejuni, Campylobacter coli, the sister group to C. jejuni, is also a significant problem, but remains a much less studied organism. The purpose of this study was to develop and apply an expanded 16 locus MLST genotyping scheme to a large collection of C. coli isolates sampled from a wide range of host species, and to complete microarray comparative genomic hybridizations for these same strains, in order to: (1) determine whether host specific clones, genotypes, or clonal complexes are evident and (2) evaluate whether there are particular genes comprising the dispensable portion of the C. coli genome that are more commonly associated with certain host species. Genotyping and ClonalFrame analyses of the expanded MLST data suggest that (1) host preferred groups have tended to evolve in the diversification of C. coli, (2) this has happened repeatedly, at different times, throughout the evolutionary history of the species, and (3) recombination has played varying roles in the diversification of the different groups. Concomitant with the information on evolutionary history derived from the MLST data, the microarray data suggests that a combination of common ancestry in some cases and lateral gene transfer in others are behind a tendency for sets of genes to be common to isolates derived from particular hosts. Keywords: comparative genomic hybridization Combimatrix CustomArray™ 4X2K was used in this study. This array is divided into 4 sectors, each of which contains 2,240 in situ synthesized oligonucleotide probes (spots) with the same probe design and layout. Based on the sequence of Campylobacter coli strain RM2228, oligonucleotide probes were designed to have a similar annealing temperature of 56ºC and a length 35-40 bp. Two separate designs were used in this study; both included 100 control probes (20 negative controls with sequences from plant and phage, each with 5 replicate spots) as well as loci from the RM2228 genome. Because of the strict criteria for probe design, not all ORFs could be covered in this analysis. The first design included 1942 of the 1967 protein coding genes described in the unfinished sequence of C. coli strain RM2228. The second-generation design was based on genes that were not clearly present (loci with low intensity or no hybridization for at least one strain) in the hybridization results involving the first design. The second design included additional two or five probes, separated from one another in order to span the entire gene, for these 615 ambiguous loci, synthesized in situ to occupy the 2,240 independent microarray spots. Replicate microarrays were hybridized for every 65 strains tested in this study.

Project description:Background: The food-borne pathogen Campylobacter is one of the most important zoonotic pathogens. Compared to other zoonotic bacteria, Campylobacter species are quite susceptible to environmental or technological stressors. This might be due to the lack of many stress response mechanisms described in other bacteria. Nevertheless, Campylobacter is able to survive in the environment and food products. Although some aspects of the heat stress response in Campylobacter (C.) jejuni are already known, information about the heat stress response in the related species C. coli and C. lari are still unknown. Results: The stress response to elevated temperatures (46°C) was investigated by survival assays and whole transcriptome analyses for the strain C. jejuni NCTC11168, C. coli RM2228 and C. lari RM2100. While C. jejuni showed highest thermotolerance followed by C. lari and C. coli, none of the strains survived at this temperature for more than 24 hours. Transcriptomic analyses revealed that only 3 % of the genes in C. jejuni and approx. 20 % of the genes of C. coli and C. lari were differentially expressed after heat stress, respectively. The transcriptomic profiles showed enhanced gene expression of several chaperones like dnaK, groES, groEL and clpB in all strains, but differences in the gene expression of transcriptional regulators like hspR, perR as well as for genes involved in metabolic pathways, translation processes and membrane components. However, the function of many of the differentially expressed gene is unknown so far. Conclusion: We could demonstrate differences in the ability to survive at elevated temperatures for C. jejuni, C. coli and C. lari and showed for the first time transcriptomic analyses of the heat stress response of C. coli and C. lari. Our data suggest that the heat stress response of C. coli and C. lari are more similar to each other compared to C. jejuni, even though on genetic level a higher homology exists between C. jejuni and C. coli. This indicates that stress response mechanisms described for C. jejuni might be unique for this species and not necessarily transferable to other Campylobacter species.

Dataset Information

Expanded MLST genotyping and comparative genomic hybridization of Campylobacter coli isolates from multiple hosts

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