FIG. 1.
Alignment of the nucleotide sequences of ISR1 and ISR2 spacers. Letters (A and E) indicate the specific primers (for rrnA and rrnE, respectively) used for the PCR amplification of the sequences. The numbers indicate the strains, and the roman numerals in parentheses indicate the subspecies to which each strain belongs. K-12 rrnE was been used as the reference strain. Nucleotides conserved in all Enterobacteriaceae studied here are labelled with an asterisk. The variable region between tRNAIle and tRNAAla of the ISR2 spacers is shown as shaded or in boldface or italics to indicate each of the three types of sequence found. Box A is underlined.