FIG. 1.

Genetic organization of the Salmonella fim gene cluster. The sizes of the polypeptides encoded by the genes are shown below the boxes. fimA (A) is the gene encoding the major fimbrial subunit, whereas fimZ (Z) and fimY (Y) are those described in the text. The arrows indicate the direction of transcription as determined by S1 nuclease mapping for fimA, primer extension analysis for fimZ and fimW (W), and sequence analysis for fimY. The derivatives of pISF101 utilized in this study are indicated below the map, with solid lines representing the DNA retained by each derivative. For pISF187, -189, and -217, the crosses indicate the locations of the inserted translation terminators.