SINGLE AMINO-ACID SUBSTITUTIONS IN THE N-TERMINUS OF VIBRIO-CHOLERAE TCPA AFFECT COLONIZATION, AUTOAGGLUTINATION, AND SERUM RESISTANCE

The toxin-coregulated pilus (TCP) of Vibrio cholerae O1 is required fo r successful infection of the host. TcpA, the structural subunit of TC P, belongs to the type IV family of pilins, which includes the PilE pi lin of Neisseria gonorrhoeae. Recently, single amino acid changes in t he N-terminus of PilE were found to abolish autoagglutination in gonoc occi. As type IV pilins demonstrate some similarities in function and amino acid sequence, site-directed mutagenesis and allelic exchange we re used to create corresponding mutations in TcpA. All four mutant str ains demonstrated autoagglutination defects, and all were highly defec tive for colonization in the infant mouse model. These results support the previously proposed correlation between autoagglutination and col onization. Finally, all four mutants are serum sensitive, indicating t hat TcpA plays a role in serum resistance, a phenotype previously attr ibuted to TcpC. As the mutations have similar effects in N. gonorrhoea e and V. cholerae, our results support the idea that type IV pilins ha ve similar functions in a variety of pathogenic bacteria.