Variation in the structural subunit and basal protein antigens of Bacteroides nodosus fimbriae

Abstract

The fimbriae of Bacteroides nodosus play a major role in protective immunity against ovine footrot and are an important determinant in the serological classification system that divides field isolates into at least eight serogroups and 16 serotypes. Purified fimbriae contain two polypeptide antigens, the structural subunit of the fimbrial strand (molecular weight about 17,000) and a basal protein (molecular weight about 80,000), both of which exhibit structural variation. Fimbriae were prepared from all prototype strains, as well as from a number of other isolates representative of each of the B. nodosus serotypes, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Substantial variation was observed in the electrophoretic mobility of the fimbrial subunits from the prototypes of each of the eight serogroups. With the exception of serogroup H, which is an unusual case, the apparent molecular weights of the fimbrial subunits ranged from about 16,500 in serogroup D to 19,000 in serogroup F (serotype 1); in serogroup A, B, C and E, the apparent molecular weights were clustered in the range of 17,000 to 17,500, whereas serogroup G was about 18,500. Serogroup H fimbriae appeared to consist of two smaller polypeptides, which in the prototype (H1) had apparent molecular weights of about 6,000 and 10,000 and which seem to have arisen as a consequence of an internal proteolytic nick in the original subunit. Electrophoretic variation in the fimbrial subunit was also observed between different serotypes, although with the exceptions of serogroups F and H, this was not as pronounced as between the serogroups. Examination of a number of isolates classified within the same serotypes showed that some variation, although minor, also occurred at this level. The basal antigen exhibited significant variation at all levels of the serotypic hierarchy in a manner apparently unrelated to the classification system. Among the range of isolates examined, the apparent molecular weight of this antigen varied from about 77,000 to 88,000.

Western blot (immunoblot) analysis of the fimbrial antigens of Bacteroides nodosus

“…The fimbrial strand of B. nodosus is comprised of a small structural protein of about 17,000 molecular weight (2,12,15,27). It has recently become evident that isolated fimbrial preparations also contain significant amounts of another polypeptide, of about 80,000 molecular weight, which appears to represent the basal protein anchoring the fimbrial strand to the cell wall (25).…”

“…It has recently become evident that isolated fimbrial preparations also contain significant amounts of another polypeptide, of about 80,000 molecular weight, which appears to represent the basal protein anchoring the fimbrial strand to the cell wall (25). Both proteins are prominent antigens in vivo and in vitro (25,28) and display variation in size among different B. nodosus isolates (2,15,19,25 (36) by the isoelectric precipitation method described previously (25) and electrophoresed on sodium dodecyl sulfate-urea gradient (8 to 15%) polyacrylamide gels with a modified Laemnmli buffer system (2,25 a The designated prototype strain of each of the serotypes is in boldface type; the prototype of each serogroup is that of the first serotype. All numbers refer to the VCS classification system (7).…”

Footrot in Clawed and Hoofed Animals: Symptoms, Causes and Treatments

“…The highly conserved amino-terminal part of the subunit is hydrophobic, whilst the variable central and carboxy-terminal region is hydrophilic (69,70). The polypeptides isolated from fimbriae range from 77 kDa to 88 kDa in size (2,68).…”

“…In serogroup H the fimbrial subunit consisted of two smaller polypeptides of 6 000 Da and 10 000 Da (2).…”

Morphogenetic expression of Moraxella bovis fimbriae (pili) in Pseudomonas aeruginosa

“…Unstained gel displays were transferred electrophoretically to nitrocellulose paper (25) and incubated with various antisera followed by 125I-protein A (0.1 ,uCi/ml) as described previously (2). Antisera were used at the following dilutions: anti-P. aeruginosa PAK/2Pfs fimbrial antiserum, 1:5,000; anti-M. bovis EPP63 fimbrial antiserum, 1:20,000.…”