BMC Genomics Research article Use of suppression subtractive hybridisation to extend our knowledge of genome diversity in Campylobacter jejuni Philip J Hepworth1, Howard Leatherbarrow2, C Anthony Hart1 and Craig Winstanley*1 Address: 1Division of Medical Microbiology and Genitourinary Medicine, University of Liverpool, Liverpool L69 3GA, UK and 2DEFRA Epidemiology Fellowship Unit, Department of Veterinary Clinical Science, Faculty of Veterinary Science, Leahurst, Wirral, UK Email: Philip J Hepworth - p.j.hepworth@liverpool.ac.uk; Howard Leatherbarrow - hleather@liverpool.ac.uk; C Anthony Hart - cahmm@liv.ac.uk; Craig Winstanley* - c.winstanley@liv.ac.uk * Corresponding author BioMed Central Open Access Published: 30 April 2007 BMC Genomics 2007, 8:110 doi:10.1186/1471-2164-8-110 This article is available from: http://www.biomedcentral.com/1471-2164/8/110 Received: 6 November 2006 Accepted: 30 April 2007 © 2007 Hepworth et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: Previous studies have sought to identify a link between the distribution of variable genes amongst isolates of Campylobacter jejuni and particular host preferences. The genomic sequence data available currently was obtained using only isolates from human or chicken hosts. In order to identify variable genes present in isolates from alternative host species, five subtractions between C. jejuni isolates from different sources (rabbit, cattle, wild bird) were carried out, designed to assess genomic variability within and between common multilocus sequence type (MLST) clonal complexes (ST-21, ST-42, ST-45 and ST-61). Results: The vast majority (97%) of the 195 subtracted sequences identified had a best BLASTX match with a Campylobacter protein. However, there was considerable variation within and between the four clonal complexes included in the subtractions. The distributions of eight variable sequences, including four with putative roles in the use of alternative terminal electron acceptors, amongst a panel of C. jejuni isolates representing diverse sources and STs, were determined. Conclusion: There was a clear correlation between clonal complex and the distribution of the metabolic genes. In contrast, there was no evidence to support the hypothesis that the distribution of such genes may be related to host preference. The other variable genes studied were also generally distributed according to MLST type. Thus, we found little evidence for widespread horizontal gene transfer between clonal complexes involving these genes. Background Infection due to Campylobacter sp. is one of the major causes of diarrheal disease worldwide and is the most common source of bacterial gastroenteritis [1]. Although transmission of Campylobacter occurs mainly through the consumption of livestock, with poultry being the most common source, C. jejuni has been isolated from diverse animal, human and environmental sources. Several recent studies have sought to determine clonal prevalences amongst isolates from these diverse sources by applying multilocus sequence typing (MLST) [2-7]. Whilst some MLST clonal complexes, such as the ST-21 complex, are widespread, others, such as the ST-61 and ST-42 com- Page 1 of 11 (page number not for citation purposes)