Based on most of the ICEs that have been examined, the excision function of an integrase is often stimulated by the presence of a closely adjacent recombination directionality factor (RDF), also termed an excisionase (Xis), that both facilitates excision and inhibits integration (Sam et al., 2004) . In our analysis, a small ORF (05SSU0904), located immediately upstream of the int gene and separated by a 14 bp intergenic region, was found to encode a possible Xis homologue with 32% aa identity to a putative excisionase (accession number AAL27447.1) from Enterococcus faecalis (Fig. 3A) . The predicted xis is preceded by a putative ribosome binding site (AGGAG), which is located 8 bp upstream from the initiation codon of xis. Further sequence analysis revealed a palindrome of 27 bp with the potential to form a stem-loop structure situated 85 bp downstream from the stop codon of int, which may function as a transcriptional terminator. The genetic organization of this locus suggests possible translational coupling between xis and int.