Temperature-inducible surface fibrillae associated with the virulence plasmid of Yersinia enterocolitica and Yersinia pseudotuberculosis.

When cultivated at 37 degrees C in static broth, human clinical isolates of Yersinia enterocolitica (serogroups O:3, O:8, and O:9) and Yersinia pseudotuberculosis (serogroup O:III) produced numerous nonflagellar surface appendages, which appeared as a lawn of fine fibrillae, each having a diameter of 1.5 to 2.0 nm and a length of 50 to 70 nm. Cultivation at 22 degrees C resulted in complete disappearance of the fibrillae. The phenotypic expression of these appendages was correlated with the presence of the 40- to 48-megadalton virulence plasmid and was strongly affected by the growth medium. Evidence is presented which suggests that these plasmid-mediated, temperature-inducible surface fibrillae are responsible for autoagglutination and are related to production of one prominent, Sarkosyl-insoluble polypeptide of ca. 180 kilodaltons in the bacterial outer membrane.