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Functional Analysis of an S-Layer-Associated Fibronectin-Binding Protein in Lactobacillus acidophilus NCFM.

Hymes JP, Johnson BR, Barrangou R, Klaenhammer TR - Appl. Environ. Microbiol. (2016)

Bottom Line: Bacterial surface layers (S-layers) are crystalline arrays of self-assembling proteinaceous subunits called S-layer proteins (Slps) that comprise the outermost layer of the cell envelope.To investigate the functional role of LBA0191 (designated FbpB) in L. acidophilus NCFM, an fbpB-deficient strain was constructed.The L. acidophilus mutant with a deletion off bpB lost the ability to adhere to mucin and fibronectin in vitro Homologues off bpB were identified in five additional putative S-layer-forming species, but no homologues were detected in species outside theL. acidophilus homology group.

View Article: PubMed Central - PubMed

Affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA.

No MeSH data available.


Related in: MedlinePlus

Schematic of the proposed interaction between FbpB and the bacterial cell surface, extracellular fibronectin, and mucin of epithelial cells.
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Figure 7: Schematic of the proposed interaction between FbpB and the bacterial cell surface, extracellular fibronectin, and mucin of epithelial cells.

Mentions: In order to determine whether FbpB is involved in adhesion to fibronectin, fbpB was deleted from the L. acidophilus NCFM genome, and the mutant was investigated for binding to fibronectin, collagen, and mucin. The fbpB-deficient strain showed significant reductions in adhesion to type III mucin and human plasma fibronectin relative to the parent strain in vitro (Fig. 4). No reduction in adhesion to type IV collagen was observed. These results demonstrated that FbpB functions as an adhesion factor by interacting specifically with fibronectin and mucin, both of which are major components of the human intestinal lining (Fig. 7) (2, 3). Attachment to the extracellular matrix provides bacteria with an improved opportunity to interact intimately with the host gastrointestinal tract (52). As transient microbes interacting with the intestinal mucosa, probiotic strains are able to affect the host by producing inhibitory substances, stimulating the immune system, and competing with pathogens for adhesion sites and nutrients (20). Transmission electron micrographs reveal a significant decrease in S-layer thickness in the ΔfbpB mutant compared to that of the parent strain (Fig. 5). S-layer thickness measurements ranged from 11.58 nm to 21.59 nm, which is consistent with previous measurements describing S-layers as being 5- to 25-nm thick (53). Previous studies have demonstrated that knockouts of the major S-layer component (SlpA) significantly reduce the adhesion of lactobacilli to intestinal cells and components of the extracellular matrix in vitro (30, 54, 55). These results suggest that the loss of FbpB may indirectly reduce adhesion ability by affecting the size of the S-layer. Aberrant S-layer thickness may further reduce adhesion ability by disrupting the attachment of SLAPs that are typically embedded in the S-layer. Overall, the cell morphology of NCK2393 was not affected by the deletion of fbpB, as shown in scanning electron micrographs (Fig. 5A). Electrophoresis of noncovalently bound extracellular proteins provides a visualization of the SLAP profiles for each strain (Fig. 6). Excluding the loss of FbpB, the banding patterns suggest no differences in the composition of the exoproteome between the mutant and parent strains.


Functional Analysis of an S-Layer-Associated Fibronectin-Binding Protein in Lactobacillus acidophilus NCFM.

Hymes JP, Johnson BR, Barrangou R, Klaenhammer TR - Appl. Environ. Microbiol. (2016)

Schematic of the proposed interaction between FbpB and the bacterial cell surface, extracellular fibronectin, and mucin of epithelial cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836419&req=5

Figure 7: Schematic of the proposed interaction between FbpB and the bacterial cell surface, extracellular fibronectin, and mucin of epithelial cells.
Mentions: In order to determine whether FbpB is involved in adhesion to fibronectin, fbpB was deleted from the L. acidophilus NCFM genome, and the mutant was investigated for binding to fibronectin, collagen, and mucin. The fbpB-deficient strain showed significant reductions in adhesion to type III mucin and human plasma fibronectin relative to the parent strain in vitro (Fig. 4). No reduction in adhesion to type IV collagen was observed. These results demonstrated that FbpB functions as an adhesion factor by interacting specifically with fibronectin and mucin, both of which are major components of the human intestinal lining (Fig. 7) (2, 3). Attachment to the extracellular matrix provides bacteria with an improved opportunity to interact intimately with the host gastrointestinal tract (52). As transient microbes interacting with the intestinal mucosa, probiotic strains are able to affect the host by producing inhibitory substances, stimulating the immune system, and competing with pathogens for adhesion sites and nutrients (20). Transmission electron micrographs reveal a significant decrease in S-layer thickness in the ΔfbpB mutant compared to that of the parent strain (Fig. 5). S-layer thickness measurements ranged from 11.58 nm to 21.59 nm, which is consistent with previous measurements describing S-layers as being 5- to 25-nm thick (53). Previous studies have demonstrated that knockouts of the major S-layer component (SlpA) significantly reduce the adhesion of lactobacilli to intestinal cells and components of the extracellular matrix in vitro (30, 54, 55). These results suggest that the loss of FbpB may indirectly reduce adhesion ability by affecting the size of the S-layer. Aberrant S-layer thickness may further reduce adhesion ability by disrupting the attachment of SLAPs that are typically embedded in the S-layer. Overall, the cell morphology of NCK2393 was not affected by the deletion of fbpB, as shown in scanning electron micrographs (Fig. 5A). Electrophoresis of noncovalently bound extracellular proteins provides a visualization of the SLAP profiles for each strain (Fig. 6). Excluding the loss of FbpB, the banding patterns suggest no differences in the composition of the exoproteome between the mutant and parent strains.

Bottom Line: Bacterial surface layers (S-layers) are crystalline arrays of self-assembling proteinaceous subunits called S-layer proteins (Slps) that comprise the outermost layer of the cell envelope.To investigate the functional role of LBA0191 (designated FbpB) in L. acidophilus NCFM, an fbpB-deficient strain was constructed.The L. acidophilus mutant with a deletion off bpB lost the ability to adhere to mucin and fibronectin in vitro Homologues off bpB were identified in five additional putative S-layer-forming species, but no homologues were detected in species outside theL. acidophilus homology group.

View Article: PubMed Central - PubMed

Affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA.

No MeSH data available.


Related in: MedlinePlus