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Purification and characterization of fimbriae from Salmonella enteritidis
Abstract:
A human isolate of Salmonella enteritidis which displayed strong pellicle formation during static broth culture and mannose-sensitive hemagglutination produced fimbriae which were morphologically indistinguishable from type 1 fimbriae of members of the family Enterobacteriaceae. Fimbrin was purified to homogeneity, and the apparent molecular weight (Mr, 14,400) was markedly lower than that reported for the type 1 fimbrin of Salmonella typhimurium (Mr, 22,100). This fimbrin contained 40% hydrophobic amino acids and lacked cysteine. The sequence of the N-terminal 64 amino acids was determined, and sequence alignment revealed that although the 18 N-terminal residues of the S. enteritidis molecule shared considerable homology with Escherichia coli and S. typhimurium type 1 fimbrins, the S. enteritidis fimbrin lacked a 6- to 9-residue terminal sequence present in the other type 1 fimbrins and, after residue 18, shared little homology with the E. coli sequence. Antibodies raised to the purified S. enteritidis fimbrin bound to surface-exposed conformational epitopes on the native fimbriae and displayed pronounced serospecificity. These antibodies were used in the isolation of a nonfimbriated Tn10 insertion mutant which was unable to hemagglutinate.
Insights
Salmonella enteritidis produces type 1 fimbriae with unique structural features. These fimbriae, distinct from other Enterobacteriaceae, are crucial for hemagglutination and bacterial adherence.
Area of Science:
- Microbiology
- Bacterial genetics
- Protein biochemistry
Background:
- Type 1 fimbriae are common surface appendages in Enterobacteriaceae, mediating adherence.
- Salmonella enteritidis, a significant human pathogen, possesses fimbriae with poorly characterized structures.
Purpose of the Study:
- To characterize the fimbriae produced by a human isolate of Salmonella enteritidis.
- To compare the fimbrin protein of S. enteritidis with those of other Enterobacteriaceae.
Main Methods:
- Static broth culture for pellicle formation and hemagglutination assays.
- Fimbriae purification, protein sequencing, and molecular weight determination.
- Antibody production and characterization for mutant isolation.
Main Results:
- S. enteritidis fimbriae were morphologically similar to type 1 fimbriae but had a lower fimbrin molecular weight (14,400 Da).
- The N-terminal sequence showed homology to E. coli and S. typhimurium fimbrins but lacked a terminal sequence and had reduced homology after residue 18.
- Antibodies against S. enteritidis fimbrin were serospecific and identified a nonfimbriated mutant.
Conclusions:
- S. enteritidis fimbrin possesses unique structural characteristics compared to other type 1 fimbrins.
- These structural differences may influence the adhesive properties and serological specificity of S. enteritidis fimbriae.
- The identified mutant provides a tool for further genetic and functional studies of S. enteritidis fimbriation.