Partial characterization of fimbriae of Xanthomonas campestris pv. hyacinthi.

Xanthomonas campestris pv. hyacinthi is a plant-pathogenic bacterium that causes yellow disease in Hyacinthus. X. c. pv.hyacinthi produces monopolarly attached fimbriae with a diameter of approximately 5 nm and a length of at least 6 micron. Fimbriae were purified by acid precipitation and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. No hemagglutinating activity of purified fimbriae was found when the fimbriae were tested with several types of erythrocytes. The fimbrial protein subunit had a relative molecular mass of 17 kDa; an isoelectric point was found at pH 4.1. Analysis of the N-terminal amino acid sequence of the fimbrial subunit indicated that X. c. pv. hyacinthi expresses type 4 fimbriae. A polyclonal rabbit antiserum was raised against the purified fimbriae. This antiserum recognized fimbriae of X. c. pv. hyacinthi in immunogold electron microscopy and immunoblotting experiments. Immunofluorescence studies showed that X. c. pv. hyacinthi cells as well as purified native fimbriae were attached to stomata of hyacinth leaves, suggesting a role for these surface antigens in the first stages of yellow disease.