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Involvement of periplasmic fibrils in motility of spirochetes
Abstract:
Nonmotile (Mot-) strains of Spirochaeta aurantia and Spirochaeta halophila were isolated with a procedure involving mutagenesis of motile wild-type cells. Electron microscopy showed that a Mot- mutant strain of S. halophia possessed incomplete periplasmic fibrils, inasmuch as most or all of the filamentous portion of the periplasmic fibrils was absent. Some of the cells of this Mot-, fibril-defective mutant strain lacked the filamentous portion of the periplasmic fibrils and formed proximal hooks, whereas other cells appeared to have a very small segment of the filamentous portion of the periplasmic fibrils attached to the proximal hooks. Motile revertants were isolated repeatedly from cultures of the Mot-, fibril-defective mutant and from S. halophila Mot- mutants that completely lacked periplasmic fibrils. The motile revertants possessed periplasmic fibrils ultrastructurally indistinguishable from wild-type periplasmic fibrils. This study indicates that periplasmic fibrils play an essential role in the motility of spirochetes.
Insights
Periplasmic fibrils are essential for spirochete motility. Studies show that nonmotile spirochete strains lacking these fibrils can regain motility when the fibrils are restored.
Area of Science:
- Microbiology
- Cell Biology
- Biophysics
Background:
- Spirochetes are a unique phylum of bacteria characterized by their helical shape and motility.
- The mechanism of motility in spirochetes, particularly the role of periplasmic fibrils, is not fully understood.
Purpose of the Study:
- To investigate the role of periplasmic fibrils in the motility of Spirochaeta aurantia and Spirochaeta halophila.
- To determine if the absence or alteration of periplasmic fibrils affects spirochete motility.
Main Methods:
- Induction of nonmotile (Mot-) mutants using chemical mutagenesis.
- Analysis of mutant strains using electron microscopy to visualize periplasmic fibrils.
- Isolation and characterization of motile revertants.
Main Results:
- Nonmotile Spirochaeta mutants exhibited defects in periplasmic fibrils, ranging from partial to complete absence of the filamentous portion.
- Some mutants with defective fibrils formed proximal hooks, suggesting a structural role.
- Motile revertants consistently showed the presence of wild-type ultrastructure of periplasmic fibrils.
Conclusions:
- Periplasmic fibrils are indispensable for the motility of spirochetes.
- The structure and integrity of periplasmic fibrils are directly linked to the ability of spirochetes to move.