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Characterization of porcine-specific surface (S-) layer protein carrying Lactobacillus species, S-layer proteins and the adhesin of Escherichia coli F18 fimbriae

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Title: Characterization of porcine-specific surface (S-) layer protein carrying Lactobacillus species, S-layer proteins and the adhesin of Escherichia coli F18 fimbriae
Author: Jakava-Viljanen, Miia
Belongs to series: 3/2007
ISSN: 1796-4660
ISBN: 952-5662-85-3 (print)952-5662-86-1 (pdf)
Abstract: The intestinal commensal microbiota of pigs comprises hundreds of different types of microorganisms (Stewart, 1997; Inoue et al., 2005). The members of the genus Lactobacillus are important residents of the gastrointestinal (GI) microbiota and have been subjects of increasing interest due to their possible role in the maintenance of GI health. Because of these putative health promoting properties, Lactobacillus species are widely used as probiotics (Ouwehand et al., 2002). One important criterion proposed for a probiotic bacterium is its ability to adhere and colonize host tissues, which enables multiplication and survival of the bacterium in the host and may prevent the colonization of pathogenic bacteria via competitive exlusion (CE). The F18 fimbriae-expressing (F18+) E. coli cause post-weaning diarrhoea (PWD) and edema disease (ED) in newly weaned piglets. The key virulence factors in diarrhoea are enterotoxins and fimbrial adhesins (Berberov et al., 2004; Zhang et al., 2006). Protection against these diseases can be established by preventing the fimbrial adhesion of these bacteria to the enterocytes of the porcine intestine. The FedF protein of F18 fimbriae was recognised as the adhesin and antibodies against FedF were found to inhibit the adhesion of F18+ E. coli to porcine enterocytes (Smeds et al., 2001; Smeds et al., 2003). However, oral immunisation with purified F18 fimbriae did not result in protection against ED by a challenge infection with F18+ verotoxigenic E. coli (VTEC) (Verdonck et al., 2007) and there are no commercial vaccines available against infections caused by F18 fimbriae-carrying E. coli strains. Like many other bacteria, several species of Lactobacillus have a surface (S-) layer as the outermost component of the cell (reviewed in Åvall-Jääskeläinen and Palva, 2005). The function of Lactobacillus S-layers characterized so far is involved in mediating adhesion to different host tissues. In addition to surface layer proteins (Slps) adhesive properties, the very large number of S-layer subunits present on the cell surface has prompted research aiming at the use of S-layers as a vehicle for the delivery of biologically active compounds, such as drug molecules, antibodies, enzymes and vaccine antigens (Sleytr et al., 2007). 13 The accurate species identification of bacteria is of fundamental importance in the development of new mucosal vaccine vectors or probiotics. Species of Lactobacillus form the most numerous genus in the heterogeneous group of lactic acid bacteria (LAB). The genus contains about one hundred described species, which are subdivided by 16S rRNA analysis, DNA-DNA hybridization and other phylogenetic methods, into eight major groups. The 16S rRNA gene is a reliable phylogenetic marker but is not an effective identification tool as it does not allow discrimination among closely related species. A multilocus sequence analysis (MLSA), on the contrary, effectively offers a high resolution and yields a robust identification system. MLSA compares the primary DNA sequences from multiple conserved protein coding loci for assessing the diversity and relation of different isolates across related taxa. The combined use of the phenylalanyl-tRNA synthase alpha subunit (pheS) and RNA polymerase alpha subunit (rpoA) gene sequences offers a reliable identification system for nearly all Lactobacillus species (Naser, 2006).
URI: http://hdl.handle.net/10138/16009
Date: 2007

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