Gene clusters for S fimbrial adhesin (sfa) and F1C fimbriae (foc) of Escherichia coli: comparative aspects of structure and function

Abstract

Fimbrial adhesins enable bacteria to attach to eucaryotic cells. The genetic determinants for S fimbrial adhesins (sfa) and for FlC ("pseudotype I") fimbriae (foc) were compared. Sfa and FlC represent functionally distinct adhesins in their receptor specificities. Nevertheless, a high degree of homology between both determinants was found on the basis of DNA-DNA hybridizations. Characteristic differences in the restriction maps of the corresponding gene clusters, however, were visible in regions coding for the fimbrial subunits and for the S-specific adhesin. While a plasmid carrying the genetic determinant for FlC fimbriae was able to complement transposon-induced sfa mutants, a plasmid carrying the genetic determinant for a third adhesin type, termed P fimbriae, was unable to do so. Proximal sfa-specific sequences carrying the S fimbrial structural gene were fused to sequences representing the distal part of thefoc gene cluster to form a hybrid cluster, and the foc proximal region coding for the structural protein was ligated to sfa distal sequences to form a second hybrid. Both hybrid clones produced intact fimbriae. Anti-FlC monoclonal antibodies (MAbs) only recognized clones which produced FlC fimbriae, and an anti-S adhesin MAb marked clones which expressed the S adhesin. However, one of four other anti-S fimbriae-speciflic MAbs reacted with both fimbrial structures, S and F1C, indicating a common epitope on both antigens. The results presented here support the view that sfa and foc determinants code for fimbriae that are similar in several aspects, while the P fimbriae are members of a more distantly related group.Fimbriae or pili are bacterial cell wall appendages which consist of about 1,000 identical protein subunits. A single fimbria is 7 nm in diameter and up to 1 ,um in length (9, 17). Very often fimbriae are associated with adhesins which enable the bacteria to attach to eucaryotic cells, including erythrocytes (RBC) (28, 31). Adherence of bacteria to eucaryotic cells is a prerequisite for many infectious diseases (27,30,41).Extraintestinal Escherichia coli isolates cause infections of the urinary tract and the blood (sepsis) and are also the causative agents of newborn meningitis (32). Such E. coli isolates may carry different types of fimbrial adhesins. P fimbriae recognize an ot-D-galactosyl-(1-4)-f3-D-galactose receptor. They are strongly associated with uropathogenic E. coli strains and can be further subdivided into nine serologically distinct groups (F71 through F13) (16,31,41). The P fimbrial gene clusters of different serogroups are functionally related. This was shown by the construction of hybrid clones consisting of DNA sequences derived from different P determinants (cis-complementation) and also by the fact that P-specific gene products were able to produce a wild-type phenotype of P insertion mutants (trans-complementation) (24,36,43,45). Another group of E. coli gene clusters, coding for type I fimbrial adhesins which interact with ct-D-mannose-containing receptors, are also complem...

Nucleotide sequence of the genes coding for minor fimbrial subunits of the F1C fimbriae of Escherichia coli

“…SfaS represents the specific adhesin binding to sialic acid (Morschhauser et al, 1990), whereas FIC fimbriae lack that specific adhesive property. The high degree of homology between the foe and sfa gene clusters was also found in previous studies (Ott et al, 1987(Ott et al, , 1988Riegman et al, 1990;Schmoll et al, in press). It strongly suggests that tlu!se gene clusters represent a family of adhesin determinants, as was observed for the P /Prs and the type 1 fimbrial adhesins ; in the P /Prs and type 1 fimbrial systems, adhesive properties have been designated for the large 35-kDa minor sub units (Lindberg et al, 1986;Klemm and Christians en , 1987;Lund et al, 1988;Riegman et al, 1988).…”

“…Genetically, FIC fimbriae have been shown to be very closely related to S fimbriae (Ott et al, 1987(Ott et al, , 1988Riegman et al, 1990). In both gene clusters, the distal part encodes minor fimbrial sub units (Hacker, 1989;Schmoll et al, 1989;Riegman et al, 1990).…”

Clonal analysis of Escherichia coli serotype O6 strains from urinary tract infections

“…This probe also detects foc specific sequences, encoding F1 C fimbriae. 17 The specific DNA probe for type 1 fimbriae gene clusters consisted of the 6.0 kb Pstl fragment of plasmid pPKL4 (Apr). 52 The aerobactin specific probe was a 7.0 kb Hindlli-Eco Rl fragment of plasmid pRG12 {Apr).…”

Virulence determinants of Escherichia coli O6 extraintestinal isolates analysed by Southern hybridizations and DNA long range mapping techniques

“…13 For differentiation of sfa and foc gene clusters the 9 kb EcoRV fragment of pANN 801-13 was used as DNA probe in Southern hybridization experiments. 13 As specific D NA probe for type 1 fimbriae gene clusters the 6.0 kb Pstl fragment of plasmid pPKL4 (Ap 1 )…”