FIG. 1.

(A) DNA sequences of the classical (top strand; GenBank accession no. X64098, bases 1250 to 1792) and El Tor (bottom strand; GenBank X74730, bases 307 to 853) tcpI-tcpP intergenic regions. Transcriptional start sites for tcpI and tcpP, as determined by primer extension, are indicated by asterisks. Putative −10 and −35 boxes are underlined. Note that the transcriptional start sites and putative promoter regions differ from those that were reported previously (23). Down arrows denote the region amplified by PCR and cloned for the tcpP::uidA promoter fusion constructs. (B) Primer extension analysis of the tcpPH transcript prepared from classical strain O395 RNA purified from cells grown to mid-log phase in ToxR-inducing conditions; the corresponding DNA sequence is also shown. Primer extension and DNA sequencing were carried out with oligonucleotide YM2.