Construction of syntactic models: Conserved amino acid blocks and positions described previously [15, 22] and with new data sets were verified or determined using MEME at http://meme.sdsc.edu/meme/meme.html. In the first step, we used motifs resulting from MEME to make MAST minings in databases at http:// meme.sdsc.edu/meme/mast.html. Since MEME motifs depend significantly on the data set use to calculate them, this approach did not enable an exhaustive detection of homologs among ascoviruses, iridoviruses, phycodnaviruses, mimiviruses and asfarviruses, and the detection sensitivity was ultimately very similar to that obtained with BLAST. To reach our detection objectives, we therefore constructed syntactic models that only included the most conserved positions and their variable spacing using WAPAM at the website. http://genoweb.univ-rennes1.fr/ Serveur-GPO/ outils_acces.php3?id_syndic=185&lang=en.