Related Experiment Video
Updated: Jul 19, 2026
The Citrobacter rodentium Mouse Model: Studying Pathogen and Host Contributions to Infectious Colitis
Published on: February 19, 2013
Use of defined mutants to assess the role of the Campylobacter rectus S-layer in bacterium-epithelial cell
B Wang1, E Kraig, D Kolodrubetz
1Department of Microbiology, University of Texas Health Science Center, San Antonio, Texas 78229, USA.
Abstract:
Campylobacter rectus is a periodontal pathogen with a 150-kDa protein on its cell surface. This protein forms a paracrystalline lattice, called the S-layer, surrounding the outer membrane of this gram-negative bacterium. To initiate a genetic analysis of the possible role of the S-layer in the initial interaction of C. rectus with host epithelial cells, C. rectus strains lacking the S-layer protein gene (crsA) were constructed by allelic exchange mutagenesis. Surprisingly, the lack of the S-layer had only a minor effect on the interaction of C. rectus with HEp-2 epithelial cells; CrsA(+) cells were 30 to 50% more adherent than were CrsA(-) bacteria. Since the host cell expression of cytokines appears to play an important role in the pathogenesis of periodontal diseases, the effect of the S-layer on the epithelial cell cytokine response was also examined by quantitative reverse transcriptase PCR and enzyme-linked immunosorbent assay. Although there were no changes in the mRNA levels for the anti-inflammatory cytokines interleukin-1 receptor agonist (IL-1ra), IL-13, and transforming growth factor beta, the expression and secretion of the proinflammatory cytokines IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) were significantly induced by both wild-type C. rectus and CrsA(-) bacteria. Interestingly, the kinetics of cytokine induction differed for the CrsA(+) and CrsA(-) bacteria. At early time points, the HEp-2 cells challenged with CrsA(-) bacteria produced higher levels of IL-6, IL-8, and TNF-alpha mRNA and protein than did cells challenged with CrsA(+) bacteria. We conclude that C. rectus may help initiate periodontitis by increasing the expression of proinflammatory cytokines and that the S-layer may temper this response to facilitate the survival of C. rectus at the site of infection.
Insights
Campylobacter rectus bacteria lacking their S-layer showed only a minor decrease in adherence to host cells. However, the S-layer appears to temper the bacterium's induction of proinflammatory cytokines, potentially aiding survival during infection.
Area of Science:
- Microbiology
- Immunology
- Periodontal disease research
Background:
- Campylobacter rectus is a known periodontal pathogen.
- The bacterium possesses a surface protein forming an S-layer, a paracrystalline lattice.
- The role of the S-layer in host-pathogen interactions and immune response is not fully understood.
Purpose of the Study:
- To investigate the role of the S-layer protein (crsA) in C. rectus adherence to host epithelial cells.
- To determine the impact of the S-layer on epithelial cell cytokine responses during infection.
- To elucidate the S-layer's contribution to the pathogenesis of periodontal disease.
Main Methods:
- Allelic exchange mutagenesis was used to create C. rectus strains lacking the S-layer gene (crsA).
- Bacterial adherence assays were performed using HEp-2 epithelial cells.
- Quantitative reverse transcriptase PCR and ELISA were employed to measure cytokine mRNA and protein levels.
Main Results:
- Strains lacking the S-layer (CrsA(-)) exhibited only a 30-50% reduction in adherence compared to wild-type (CrsA(+)) bacteria.
- Both CrsA(+) and CrsA(-) bacteria significantly induced proinflammatory cytokines (IL-6, IL-8, TNF-alpha).
- CrsA(-) bacteria induced higher levels of proinflammatory cytokines at early time points compared to CrsA(+) bacteria.
Conclusions:
- C. rectus initiates periodontitis by inducing proinflammatory cytokine expression.
- The S-layer may temper the host's inflammatory response, facilitating bacterial survival at the infection site.
- The S-layer influences the kinetics of cytokine induction by C. rectus.
