Browsing by Author "Wikman, Helena"

Surface (S-) layers, structural entities that surround the cell envelope of various bacteria, are comprised of a porous lattice of identical protein or glycoprotein subunits. Interestingly, the S-layer is able to promote adherence to host epithelial cells in a variety of Lactobacillus species. L. amylovorus DSM 16698, a strain of porcine origin, encodes at least three putative types of S-layer proteins in its genome sequence. In this study the surface structure of L. amylovorus DSM 16698 strain and the adhesion properties of its S-layer proteins to porcine intestinal epithelial IPEC-1 cell line were examined based on preliminary results. In addition, host receptors potentially specific for S-layer proteins were isolated from IPEC-1 cells. Cloned recombinant S-layer proteins rSlpA and rSlpB of DSM 16698 were reassembled onto fluorescent-labeled L. amylovorus cell wall extracts as a means to mimic the native S-layer lattice structure. Adhesion between the reassembled recombinant S-layer complexes and IPEC-1 cells was assessed qualitatively by microscopy and quantitatively by measuring fluorescence intensity. Results from in vitro adhesion assays indicate that the rSlpA and rSlpB proteins both mediated the adherence of the L. amylovorus DSM 16698 strain to porcine intestinal epithelial cells. Antibodymediated adhesion inhibition experiments were also performed, in which the two rSlps were pretreated with their specific anti-rSlp serum, and showed that adhesion between the rSlps and IPEC-1 cells could be inhibited by the antibody treatment. Moreover, by using fluorescent-labeled rSlp-specific antibody, the surface structure of L. amylovorus cells was microscopically examined. With this immunofluorescent technique, the SlpA and SlpB proteins were both observed to localize on the cell surface and exhibit a similar distribution pattern. Putative S-layer host cell receptors were isolated from the interaction between the reassembled rSlp/cell wall complexes and IPEC-1 derived membrane proteins using a SDS-PAGE-based system. Receptor isolation experiments resulted in repeatedly the same protein profile. It has previously been shown that L. amylovorus DSM 16698 attaches to IPEC-1 cells, but the identities of surface-localized components that mediate this microbe-host interaction had yet to be determined. In this present study, S-layer proteins were found to be an important mediator in the interaction between L. amylovorus DSM 16698 and a porcine epithelial cell line. Additionally, it was shown how S-layer proteins are localized on the surface of L. amylovorus DSM 16698 cells.