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Type 1 fimbriae of Salmonella enteritidis
K H Müller1, S K Collinson, T J Trust
1Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
Abstract:
Salmonella enteritidis was previously shown to produce fimbriae composed of 14,000-molecular-weight (Mr) fimbrin monomers (J. Feutrier, W. W. Kay, and T. J. Trust, J. Bacteriol. 168:221-227, 1986). Another distinct fimbrial structure, comprising 21,000-Mr fimbrin monomers, has now been identified. These fimbriae are simply designated as SEF 14 and SEF 21, respectively (for S. enteritidis fimbriae and the Mr [in thousands] of the fimbrin monomer). A simple method for the purification of both structures was developed by using the different biochemical properties of these fimbriae. SEF 21 remained intact after being boiled in sodium dodecyl sulfate but readily dissociated into subunits of 21,000 Mr at pH 2.2. The overall amino acid composition and the N-terminal amino acid sequence of the SEF 21 fimbrin were distinct from those of SEF 14 but were virtually identical to the predicted sequence for type 1 fimbrin of Salmonella typhimurium. Immunoelectron microscopy of S. enteritidis clearly revealed fimbrial structures that reacted with immune serum specific to the 21,000-Mr fimbrin. Immune sera raised against this subunit were cross-reactive with type 1 fimbrins found in whole-cell lysates of S. typhimurium, Salmonella illinois, and Salmonella cubana. However, there was no cross-reaction with Escherichia coli type 1 fimbriae or with other fimbrins produced by S. enteritidis. Under certain growth conditions, S. enteritidis produced both SEF 14 and SEF 21. However, when S. enteritidis was grown at 30 degrees C or lower, only the 21,000-Mr SEF 21 fimbrin could be detected. There was a direct correlation between mannose-sensitive hemagglutination and the presence of SEF 21.
Insights
Salmonella enteritidis produces two fimbriae: SEF 14 and SEF 21. SEF 21, a distinct fimbrial structure, is associated with mannose-sensitive hemagglutination and shares similarities with Salmonella typhimurium type 1 fimbriae.
Area of Science:
- Microbiology
- Bacteriology
- Structural Biology
Background:
- Salmonella enteritidis is known to produce fimbriae composed of 14,000-molecular-weight (Mr) fimbrin monomers (SEF 14).
- A second distinct fimbrial structure composed of 21,000-Mr fimbrin monomers (SEF 21) has been identified in S. enteritidis.
Purpose of the Study:
- To characterize the novel SEF 21 fimbrial structure from Salmonella enteritidis.
- To compare SEF 21 with previously identified fimbriae and related structures in other Salmonella species and Escherichia coli.
Main Methods:
- Purification of SEF 14 and SEF 21 fimbriae using differential biochemical properties.
- Analysis of fimbrial subunit composition, including amino acid sequencing.
- Immunoelectron microscopy and serological cross-reactivity assays.
- Investigation of fimbrial expression under different growth conditions and correlation with hemagglutination.
Main Results:
- A simple purification method for SEF 14 and SEF 21 was developed.
- SEF 21 fimbriae are composed of 21,000-Mr subunits, distinct from SEF 14.
- SEF 21 fimbrin shares high similarity with Salmonella typhimurium type 1 fimbrin.
- Immune sera against SEF 21 cross-react with type 1 fimbriae of S. typhimurium, S. illinois, and S. cubana, but not E. coli.
- SEF 21 expression is favored at temperatures above 30°C and correlates directly with mannose-sensitive hemagglutination.
Conclusions:
- Salmonella enteritidis possesses at least two distinct fimbrial types, SEF 14 and SEF 21.
- SEF 21 represents a type 1 fimbria homologous to that of Salmonella typhimurium.
- The presence of SEF 21 is linked to mannose-sensitive hemagglutination and specific Salmonella serotypes.