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Growth in and breakdown of purified rabbit small intestinal mucin by Yersinia enterocolitica
1Department of Medical Biochemistry, Health Sciences Centre, Calgary, Alberta, Canada.
Abstract:
The mucus lining of the gastrointestinal tract serves as a protective barrier over the epithelial surface that must be crossed by invading bacteria seeking entry into the mucosa. The gel-forming component of mucus is mucin, a large polymeric glycoprotein. The present study examined the growth of Yersinia enterocolitica (with and without its virulence plasmid) in purified rabbit small intestinal mucin and the ability of bacteria to degrade mucin. Both virulent and nonvirulent organisms showed enhanced growth in mucin-supplemented media compared with unsupplemented media, but only at 37 degrees C and not at 25 degrees C. The effects of mucin were not specific because medium supplemented with bovine serum albumin also enhanced bacterial growth at 37 degrees C. Purified mucin was broken down into lower-molecular-weight components (assessed by monitoring its elution profile on a Sepharose CL-2B column) by plasmid-bearing Y. enterocolitica but not by plasmid-cured organisms. Culturing virulent Y. enterocolitica at 25 degrees C completely suppressed its capacity to degrade mucin, suggesting that this activity depends on plasmid expression. These results were confirmed in similar studies with purified rabbit colonic mucin. Mucin-degrading activity could be demonstrated in spent culture media from virulent Y. enterocolitica incubated at 37 degrees C but not in bacterial membrane preparations. Changes in the elution profiles of small intestinal and colonic mucins exposed to plasmid-bearing Y. enterocolitica at 37 degrees C were consistent with proteolytic depolymerization. The ability to grow well in mucin may help Y. enterocolitica to colonize the intestine, while the production of a mucin-degrading enzyme(s) by plasmid-bearing organisms may assist pathogenic strains to solubilize and penetrate the mucus gel layer.
Insights
Yersinia enterocolitica grows better in mucin, especially virulent strains that can degrade it. This mucin degradation, dependent on the virulence plasmid and temperature, may help bacteria colonize the gastrointestinal tract.
Area of Science:
- Microbiology
- Gastroenterology
- Biochemistry
Background:
- The gastrointestinal tract is protected by a mucus layer composed of mucin glycoproteins.
- Bacteria must penetrate this mucus barrier to invade the host mucosa.
- Yersinia enterocolitica is a pathogen that invades the gastrointestinal tract.
Purpose of the Study:
- To investigate the growth of Yersinia enterocolitica in mucin.
- To determine the ability of Y. enterocolitica to degrade mucin.
- To understand the role of the virulence plasmid in mucin degradation and bacterial growth.
Main Methods:
- Culturing virulent and nonvirulent Yersinia enterocolitica in media supplemented with purified rabbit small intestinal and colonic mucin.
- Assessing bacterial growth at different temperatures (25°C and 37°C).
- Analyzing mucin degradation by monitoring changes in mucin elution profiles using Sepharose CL-2B chromatography and detecting mucin-degrading activity in culture supernatants.
Main Results:
- Both virulent and nonvirulent Y. enterocolitica showed enhanced growth in mucin-supplemented media at 37°C, but not at 25°C.
- Plasmid-bearing (virulent) Y. enterocolitica degraded mucin into lower-molecular-weight components, while plasmid-cured (nonvirulent) strains did not.
- Mucin degradation by virulent Y. enterocolitica was dependent on temperature and virulence plasmid expression, with activity suppressed at 25°C.
- Mucin-degrading activity was found in spent culture media, not bacterial membrane preparations.
Conclusions:
- Yersinia enterocolitica exhibits enhanced growth in mucin, potentially aiding intestinal colonization.
- Virulent Y. enterocolitica possesses the ability to degrade mucin, a function dependent on its virulence plasmid and optimal temperature (37°C).
- This mucin-degrading capability may facilitate pathogenic strains' ability to solubilize and penetrate the protective mucus layer, contributing to infection.
