REGULATION OF TCP GENES IN CLASSICAL AND EL-TOR STRAINS OF VIBRIO-CHOLERAE O1

Expression of genes encoding the toxin-co-regulated pilus (TCP) varies between the two biotypes of Vibrio cholerae O1. Sequence analysis of the tcp locus from the classical and El Tor strains has revealed diffe rences in the intergenic regions between tcpI and tcpP, and tcpH and t cpA, which may be involved in regulation. To investigate this possibil ity, transcription of tcpA, and the predicted upstream promoters for t cpI and tcpP, has been analysed in the classical and El Tor strains us ing promoter-cat (chloramphenicol acetyltransferase) fusions. Together with primer extension analyses, these studies indicate that the tcpA and tcpP promoters are toxR-dependent and suggest that TcpP may be inv olved in activation of both the tcpI and rcpP promoters. We conclude t hat differences in the level of tcpA expression in a classical and an El Tor strain are likely to be due to the effect of sequence variation on the ability of control factors to act on these regulatory regions.