Comparative analysis of the whole set of rRNA operons between an enterohemorrhagic Escherichia coli O157 : H7 Sakai strain and an Escherichia coli K-12 strain MG1655

Two primer sets for direct sequence determination of all seven rRNA operons (rrn)) of Escherichia coli have been developed; one is for specific-amplif ication of each nn operon and the other is for direct sequencing of the amp lified operons. Using these primer sets, we determined the nucleotide seque nces of seven rrn operons, including promoter and terminator regions, of an enterohemorrhagic E. coli (EHEC) O157:H7 Sakai strain. To elucidate the in tercistronic or intraspecific variation of rin operons, their sequences wer e compared with those for the K-12 rrn operons. The rrn genes and the inter nal transcribed spacer regions showed a higher similarity to each other in each strain than between the corresponding operons of the two strains. Howe ver, the degree of intercistronic homogeneity was much higher in the EHEC s train than in K-12. In contrast, promoter and terminator regions in each op erons were conserved between the corresponding operons of the two strains, which exceeded intercistronic similarity.