Identification and sequence analysis of lpfABCDE, a putative fimbrial operon of Salmonella typhimurium

Abstract

A chromosomal region present in Salmonella typhimurium but absent from related species was identified by hybridization. A DNA probe originating from 78 min on the S. typhimurium chromosome hybridized with DNA from Salmonella enteritidis, Salmonella heidelberg, and Salmonella dublin but not with DNA from Salmonella typhi, Salmonella arizonae, Escherichia coli, and Shigella serotypes. Cloning and sequence analysis revealed that the corresponding region of the S. typhimurium chromosome encodes a fimbrial operon. Long fimbriae inserted at the poles of the bacterium were observed by electron microscopy when this fimbrial operon was introduced into a nonpiliated E. coli strain. The genes encoding these fimbriae were therefore termed lpfABCDE, for long polar fimbriae. Genetically, the lpf operon was found to be most closely related to the fim operon of S. typhimurium, both in gene order and in conservation of the deduced amino acid sequences.All members of the family Enterobacteriaceae express fimbriae, or pili, which allow them to attach to host surfaces. This attachment is the first step in the colonization of their preferred host niche. The various fimbrial adhesins were originally distinguished by their receptor specificity. Hemagglutination of erythrocytes was used as a criterion to define three fimbrial classes (for a recent review, see reference 14). Fimbriae whose agglutination is prevented by coincubation with D-mannose were designated type 1 fimbriae (41). Type 2 fimbriae, a nonhemagglutinating fimbrial class, were later found to resemble nonadhesive variants of type 1 fimbriae (20,36,43). Finally, pili able to agglutinate animal erythrocytes only after the erythrocytes have been treated with tannic acid were designated type 3 fimbriae (22, 23). This early classification was supported by data on the morphological characteristics of these fimbriae. Type 1 and type 2 fimbriae have a width of 7 to 8 nm and display a channeled rodlike appearance due to the arrangement of subunits around a hollow core (43). Type 3 fimbriae are 4 to 5 nm in diameter and lack an axial hole on the basis of electron microscopic examination (42). Recently, thin fimbriae (3 to 4 nm) with a unique curly morphology in members of the Enterobacteriaceae have been described (4,44). A comparison of sequence data obtained from several fimbrial systems with similar morphologies revealed that the major fimbrial subunits of curly fimbriae show a high degree of sequence conservation. These fimbriae are therefore now considered to form a distinct fimbrial class. The designation GVVPQ has been proposed, in reference to a short amino acid sequence conserved at the N terminus of their major fimbrial subunit (19). Type 1, type 2, type 3, and GVVPQ fimbriae have the common characteristic that their fimbrial subunits contain signal sequences which are cleaved by signal peptidase I. In contrast, a fifth enterobacterial class of pili, termed type 4 fimbriae, has been shown to use a different export system for translocation of its fimbrial subunits across t...

Chaperone–usher pathways: diversity and pilus assembly mechanism

“…FimH forms part of the tip fibrillum in type I fimbriae and is the adhesive structure responsible for interaction with D-mannosylated proteins such as epithelial bladder and kidney cells [15] or uroplakins [16,17] (table 1). FimH was also the first structure to be determined, consisting of two subdomains: an N-terminal lectin domain containing the mannose-binding site, connected via a linker chain to a C-terminal pilin domain responsible for incorporating FimH into the fimbrial structure [18].…”

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

“…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].…”

“…Contact of Typhimurium with cultured MDCK cells induced transient expression of an ill-defined surface appendage [8] and the long polar fimbrial (LPF) structure elaborated by Typhimurium [9] was shown to mediate adhesion of Typhimurium to Peyer's patches [10]. The 'virulence' plasmid of salmonella, more accurately described as serotype associated plasmid (SAP) [11] and this term will be used throughout this paper, has been shown to contribute to the systemic phase of Typhimurium infection of murines [12] and of Dublin infections of bovines [13].…”

Occurrence of virulence-related sequences and phylogenetic analysis of commensal and pathogenic avian Escherichia coli strains (APEC)

“…Gene lpfA O157/ OI154 is one of the four genetic variants of lfpA gene identified in STEC (Toma et al, 2004) and in other diarrheagenic E. coli strains (Toma et al 2006). The lpfA encodes for the variants of the long polar fimbriae (LPF) that are adhesins related to Type 1 fimbriae, first identified in Salmonella enterica serovar Typhimurium (Bäumler et al 1995). The higher frequency of lpfA O157/OI154 among pathogenic avian E. coli analyzed in this work suggest that LPF could be a member of the colonization factors presented in these strains that are responsible for the adherence capacity described in previous studies (Silveira et al 2002b, Amabile de Campos et al 2005.…”