SEQUENCE-ANALYSIS OF THE VIBRIO-CHOLERAE ACFD GENE REVEALS THE PRESENCE OF AN OVERLAPPING READING FRAME, ORFZ, WHICH ENCODES A PROTEIN THATSHARES SEQUENCE SIMILARITY TO THE FLIA AND FLIC PRODUCTS OF SALMONELLA

The nucleotide (nt) sequence of the Vibrio cholerae acfD gene (encodin g an accessory colonization factor) has been determined. The acfD gene encompasses 254 nt that are predicted to encode an 88-amino-acid (aa) protein. Additionally, an open reading frame of 184 aa, designated or fZ, was detected that overlaps the 3' end of acfD by 45 nt. Computer-a ssisted homology searches revealed that OrfZ possesses aa sequence sim ilarity to the C terminus of the fliC product of Salmonella muenchen a nd S. rubislaw. Additionally, OrfZ shares limited aa sequence similari ty to a region of the S. typhimurium fliA product. Interestingly, a V. cholerae acfD::TnphoA mutant demonstrates reduced motility and an alt ered swarming phenotype in semi-solid media when compared to wild-type V. cholerae. The possibility that the reduced motility and altered mo rphology result from polar effects on orfZ expression is currently bei ng investigated.