Genome Sequence of Efaecalis

The genome of E.faecalis V583 is 3.2 Mbp and contains three plasmids, pTEF1, pTEF2, and pTEF3, which are 66.3kbp, 57.6kbp, and 17.9kbp, respectively. The total genome encodes 3337 predicted open reading frames (ORFs), of which one-quarter comprise mobile elements and acquired DNA, including a 150-kbp pathogenicity island [9]. As E.faecalis V583 is the only E.faecalis isolate sequenced to date, it is uncertain whether these characteristics are also true of other isolates from this bacterial genus. The genome sizes of other E.faecalis strains have previously been mapped and were estimated to range from 2825 kbp to 3250kbp [10, 11]. Strain-specific variability in gene content and genomic organization may account for the differences in pathogenicity in some bacterial isolates. Comparison of E. coli K-12 with E. coli OH157:H7 found 1500 ORFs specific to OH157:H7 [12], while comparative differences in three Listeria monocytogenes strains noted between 51 and 97 strain-specific genes [13].

Encoded on the pathogenicity island are genes for cytolysin, enterococcal surface protein (Esp), and other putative virulence or adaptation genes, and this region of DNA has an atypical G+C content (32.2%). In E.faecalis V583 (EF0479-EF0628), the previously described pathogenicity island contains a 17-kbp deletion (ORFs EF0047-EF0057), an IS256-like insertion in cylB, and an insertion of an IS905-like element. In addition, a 2.8-kbp region possessing the features of a group II intron (EF0012) is absent.11

As previously noted, 85% of the E. faecalis V583 ORFs share their greatest homology with other low G+C gram-positive bacteria; however, there is no large-scale synteny to any other genome in this group, which is probably due to the large amount of mobile DNA elements present in the E.faecalis genome [8]. A feature E. faecalis does share with this group is a strong transcriptional skew, with 90% of the ORFs in E.faecalis aligned to the direction of replication.

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