Unique fimbriae‐like structures encoded by sefD of the SEF14 fimbrial gene cluster of Salmonella enteritidis

Abstract

The SEF14 gene cluster of Salmonella enteritidis was recently shown to contain three genes, sefABC, encoding a unique fimbrin, and proteins homologous to fimbrial chaperones and outer membrane proteins (ushers), respectively. A fourth open reading frame, designated sefD, was found immediately downstream of sefABC and overlapping sefC. The translated protein sequence of sefD was unique, but the composition was similar to that of other bacterial fimbriae. SefD was produced in abundance by wild-type S. enteritidis as shown by Western blot analysis using antibodies raised to affinity-purified, recombinant SefD. Furthermore, unusually long, thin, fimbriae-like structures were evident on S. enteritidis and Escherichia coli by immunoelectron microscopy, but in other bacterial species SefD was expressed as amorphous material. Therefore, in S. enteritidis and E. coli, SefD is the predominant structural subunit of SEF18. The SEF18 fimbriae-like structures were shown to be serologically distinct from the three known S. enteritidis fimbriae SEF14, SEF17 and SEF21. Furthermore, SEF18 was still produced in sefA insertion mutants, indicating that SEF14 and SEF18 were structurally distinct. Thus, the SEF14 gene cluster is the first example in the Enterobacteriaceae of a gene cluster that encodes two fimbrin-like proteins, which are assembled into two distinct cell-surface structures, SEF14 and SEF18. DNA hybridization and Western blot analyses showed that SefD was widely distributed among the Enterobacteriaceae and was present in E. coli, Shigella, Enterobacter, Citrobacter, Erwinia, Hafnia, Klebsiella, Providencia, and Proteus but not in the non-Enterobacteriaceae Gram-negative bacteria Pseudomonas and Aeromonas, or in Gram-positive bacteria Bacillus or Staphylococcus.(ABSTRACT TRUNCATED AT 250 WORDS)

Genomic analysis and growth-phase-dependent regulation of the SEF14 fimbriae of Salmonella enterica serovar Enteritidis The GenBank accession number for the sequence reported in this paper is AF239978.

“…Genomic DNA was also probed with a sefD-specific PCR product. Both these techniques suggested that sefD, unlike sefABC, had a widespread distribution among enteric bacteria (Clouthier et al, 1994). Several lines of evidence refute this distribution.…”

“…The SEF14 fimbriae require four proteins for biogenesis : the major subunit (SefA), chaperone (SefB) and usher (SefC) have previously been characterized (Clouthier et al, 1993 ;Thorns et al, 1990 ;Turcotte & Woodward, 1993). The minor subunit (SefD) was also previously identified but not thought to be part of the SEF14 fimbriae (Clouthier et al, 1994). We recently reported the role of the SEF14 fimbriae in virulence and showed that SEF14 fimbriae are essential for binding to macrophages (Edwards et al, 2000).…”

Distribution, gene sequence and expressionin vivoof the plasmid encoded fimbrial antigen ofSalmonellaserotype Enteritidis

“…The SEF14 fimbrial structure [24][25][26][27] was implicated in persistent infection in the chicken [28,29]. The genetic determinants of the SEF'D' fimbrial structure, also referred to as SEF18, were colocated with the genes encoding SEF14 [30] but as yet no demonstrable phenotype has been ascribed to the SEF'D' fimbrial structure. Genetic evidence that Enteritidis isolates encode lpf and bfplike sequences has been gained also [7,9].…”

Multiplex-PCR Assay for Detection of some Major Virulence Genes of <i>Salmonella enterica</i> Serovars from Diverse Sources

“…However, it was not detected in many of the isolates tested by microarray analysis. The stn gene has been proposed as a putative virulence factor and causative agent of diarrhoea 6 . Detection of stn gene was reported in all the strains of S. enterica, but not in S. Bongori 7 .…”

“…Some genes such as inv, sef, etc. are involved in adhesion and invasion 5,6 , while others are like mgtC5 associated with survival in the host system, or in the actual manifestation of pathogenic processes, viz. sop, stn, pip A, B, D, etc.…”