Large scale variation in Enterococcus faecalis illustrated by the genome analysis of strain OG1RF
1 Division of Infectious Diseases, Department of Medicine, University of Texas Medical School, Houston, Texas 77030, USA
2 Center for the Study of Emerging and Re-emerging Pathogens, University of Texas Medical School, Houston, Texas 77030, USA
3 Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030, USA
4 Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
5 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
6 Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030, USA
Genome Biology 2008, 9:R110 doi:10.1186/gb-2008-9-7-r110Published: 8 July 2008
Enterococcus faecalis has emerged as a major hospital pathogen. To explore its diversity, we sequenced E. faecalis strain OG1RF, which is commonly used for molecular manipulation and virulence studies.
The 2,739,625 base pair chromosome of OG1RF was found to contain approximately 232 kilobases unique to this strain compared to V583, the only publicly available sequenced strain. Almost no mobile genetic elements were found in OG1RF. The 64 areas of divergence were classified into three categories. First, OG1RF carries 39 unique regions, including 2 CRISPR loci and a new WxL locus. Second, we found nine replacements where a sequence specific to V583 was substituted by a sequence specific to OG1RF. For example, the iol operon of OG1RF replaces a possible prophage and the vanB transposon in V583. Finally, we found 16 regions that were present in V583 but missing from OG1RF, including the proposed pathogenicity island, several probable prophages, and the cpsCDEFGHIJK capsular polysaccharide operon. OG1RF was more rapidly but less frequently lethal than V583 in the mouse peritonitis model and considerably outcompeted V583 in a murine model of urinary tract infections.
E. faecalis OG1RF carries a number of unique loci compared to V583, but the almost complete lack of mobile genetic elements demonstrates that this is not a defining feature of the species. Additionally, OG1RF's effects in experimental models suggest that mediators of virulence may be diverse between different E. faecalis strains and that virulence is not dependent on the presence of mobile genetic elements.