Conservation of O157 Sakai genes in O157 and non-O157 EHEC strains. The data from CGH analyses of O157 and non-O157 EHEC strains using an O157 Sakai oligoDNA microarray are summarized. Among the 4,905 singleton genes on the O157 Sakai genome, 3,651 were categorized as 'conserved in K-12', 101 as 'partly conserved in K-12', and 1,153 as 'Sakai-specific'. Among the 151 repeated gene families, 23 were categorized as 'conserved in K-12' and 128 as 'Sakai-specific'. Genes that were judged as 'present' in all the tested strains were categorized as 'Fully conserved' genes, those judged as 'absent' in all the strains as 'Fully absent' genes, and others as 'Variably absent or present' genes. In the CGH analysis, because repeated gene families with reduced copy numbers were often judged as 'absent', all the repeated gene families judged as 'absent' were categorized as 'uncertain'. See Additional data file 4 for further details.