FIG. 1.

Diagram of allelic exchange between a mutant fimH allele (fimH∗) carried on the nonreplicating vector pKAS32 and the fim region on the chromosome of strain ORN208. Following introduction of the plasmid by mating (28), recombinants were selected and scored for the phenotypic characteristics noted. Recombinants that had deletions (Δ) of the vector and the original fimH insertion mutation in ORN208 were identified by selection on streptomycin-containing agar and scored for the appropriate antibiotic and hemagglutination phenotype as indicated. Each fimH lesion introduced was more than 98% linked (by P1 transduction [18]) to the tetR insertion adjacent to fimH. Phenotypic designations denote sensitivity (s) or resistance (r) to antibiotics as follows: Nal, nalidixic acid; Kan, kanamycin; Tet, tetracycline; Amp, ampicillin; Str, streptomycin. Erythrocyte or yeast cell agglutination is collectively denoted phenotypically as Hag. Streptomycin sensitivity is conferred by the rpsL gene, kanamycin resistance is conferred by the neoR gene, ampicillin resistance is conferred by the bla gene, and tetracycline resistance is conferred by the tetR gene.