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Basic characterization of W-pili
Abstract:
The bacterial drug-resistance plasmids Sa, R388 and R7K that comprise the W compatability group were transferred by conjugation to species in the genera Escherichia, Salmonella, Shigella and Pseudomonas, chosen for their lack of common pili. On receiving the W plasmids, all strains produced pili, which were similar morphologically, at average frequencies of up to 3-0 pila/cell. The pili determined by the W plasmids were also related serologically, but unrelated to those of other plasmids. R- segregant strains which had lost their plasmids showed a simultaneous loss of both pili and drug-resistance characteristics. W-pili are pointed flexible filaments 10 to 12 nm thick, with an average length of 450 nm. The best host found was Salmonella typhimurium.
Insights
Bacterial W plasmids confer drug resistance and enable pili production in new hosts like Escherichia and Salmonella. Loss of these plasmids results in the simultaneous loss of pili and drug resistance.
Area of Science:
- Microbiology
- Bacterial genetics
- Plasmid biology
Background:
- Drug-resistance plasmids are critical in bacterial evolution and spread.
- The W compatibility group plasmids (Sa, R388, R7K) are known to confer drug resistance.
- The role of these plasmids in pilus formation was not fully understood.
Purpose of the Study:
- To investigate the role of W plasmids in pilus formation in various bacterial species.
- To characterize the pili produced under the influence of W plasmids.
- To establish a correlation between plasmid carriage, pilus production, and drug resistance.
Main Methods:
- Conjugation was used to transfer W plasmids (Sa, R388, R7K) to recipient bacteria (Escherichia, Salmonella, Shigella, Pseudomonas).
- Recipient strains were selected for their lack of common pili.
- Pilus morphology, frequency, and serological relationships were analyzed.
- Loss of plasmids and associated traits was assessed in segregant strains.
Main Results:
- All recipient strains acquired pili upon W plasmid transfer, with an average frequency of up to 3.0 pili/cell.
- The W-plasmid-determined pili were morphologically similar across different hosts and serologically related to each other, but distinct from pili of other plasmids.
- Segregant strains that lost the W plasmids simultaneously lost both pilus production and drug resistance.
- W-pili were described as pointed, flexible filaments (10-12 nm thick, 450 nm long).
- Salmonella typhimurium was identified as the most effective host for W plasmid transfer and pilus expression.
Conclusions:
- W plasmids are responsible for the production of specific pili (W-pili) in diverse bacterial genera.
- Pilus formation is directly linked to the presence of W plasmids and their associated drug resistance.
- W-pili represent a novel class of pili with distinct characteristics, potentially influencing bacterial interactions and fitness.