Campylobacter coli VC167 T2 has two flagellin genes, flaA and flaB, which share 91.9% sequence identity. TheflaA gene is transcribed from a r28 promoter, and theflaB gene from a cS4 promoter. Gene replacement mutagenesis techniques were used to generate flaA flaB and flaA flaB+ mutants. Both gene products are capable of assembling independently into functional filaments. A flagellar filament composed exclusively of the JaA gene product -is indistinguishable in length from that of the wild type and shows a slight reduction in motility. The flagellar filament composed exclusively of theflaB gene product is severely truncated in length and greatly reduced in motility. Thus, while both flagellins are not necessary for motility, both products are required for a fully active flageilar filament. Although the wld-type flageliar filament is a heteropolymer of the flaA and flaB gene products, immunogold electron microscopy suggests that flaB epitopes are poorly surface exposed along the length of the wild-type filament.

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An easily constructed and inexpensive template has been developed, which enables the fluorescent-antibody technique to be applied to serial dilutions and allows 18 assays on a single microscope slide.