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Title: Campylobacter fetus subspecies contain conserved type IV secretion systems on multiple genomic islands and plasmids

item VAN DER GRAAF, LINDA - Utrecht University
item Miller, William - Bill
item Yee, Emma
item GORKIEWICZ, GREGOR - Medical University Of Graz
item FORBES, KENNETH - University Of Aberdeen
item ZOMER, ALDERT - Utrecht University
item WAGENAAR, JAAP - Utrecht University
item DUIM, BRIGITTA - Utrecht University

Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2016
Publication Date: 4/6/2016
Citation: Van Der Graaf, L., Miller, W.G., Yee, E., Gorkiewicz, G., Forbes, K., Zomer, A.L., Wagenaar, J., Duim, B. 2016. Campylobacter fetus subspecies contain conserved type IV secretion systems on multiple genomic islands and plasmids. PLoS One. 11(4):e0152832..

Interpretive Summary: The food-borne pathogen Campylobacter is a natural contaminant of most birds and livestock. Campylobacter fetus strains are associated normally with livestock disease and are one of the leading causes of abortions in cattle and sheep. Campylobacter fetus currently contains three defined subspecies: C. fetus subsp. fetus, C. fetus subsp. venerealis and C. fetus testudinum. These subspecies are distinguished by their host range and pathogenicity: C. f. fetus is isolated from different animals and occasionally food, C. f. venerealis is restricted to cattle and is a leading cause of abortions in cattle, and C. f. testudinum is isolated from reptiles and occasionally from human systemic infections. Genomic islands associated with virulence in these strains have been identified previously. This study characterizes these islands from 27 C. fetus strains. Results indicated that at least three distinct types of islands are present within this species, some strains contain multiple virulence islands and while some islands are present chromosomally, some are present extra-chromosomally, suggesting that these islands could be transmitted from strain to strain.

Technical Abstract: The features contributing to the differences in pathogenicity of the C. fetus subspecies are unknown. Putative factors involved in pathogenesis are located in genomic islands that encode type IV secretion system (T4SS) and fic-domain (filamentation induced by cyclic AMP) proteins. In the genomes of 27 C. fetus strains, three phylogenetically-different T4SS-encoding regions were identified: one was located in both the chromosome and extra-chromosomal plasmids; one was located exclusively in the chromosome; and one exclusively in extra-chromosomal plasmids. It was shown that C. fetus genomes can contain multiple T4SSs and that homologous T4SSs can be found on the chromosomes and plasmids within one C. fetus strain. Comparative analysis showed that T4SSs with a similar location were conserved in sequences and gene order between the C. fetus genomes. The chromosomal T4SSs were located in genomic islands and these islands differed mainly in the presence of insertion sequences, phage related genes and hypothetical proteins. The 27 C. fetus genomes contained multiple fic-domain genes and at least nine phylogenetic clusters of fic genes were identified. The T4SS and fic genes were found in C. fetus strains of both subspecies fetus and venerealis, and the differences in the presence of T4SS and fic genes were not associated with geographical origin of the strains.