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Identification of restriction barriers in Pasteurella multocida
1Institute for Animal Health, Compton, Berks, UK.
Abstract:
Several naturally occurring antibiotic resistance plasmids were isolated from Pasteurella multocida type D strains. One plasmid, pPM1, was used to study transfer of DNA among P. multocida strains, and could be transferred into Escherichia coli and some P. multocida isolates. However, pPM1 could only be transferred into the toxigenic P. multocida LFB3 at very low frequency. Plasmid recovered from the electrotransformants could be transferred to LFB3 at high frequency. These plasmid DNAs were resistant to PstI, and sensitive to DpnI digestion. Sensitivity to DpnI was common to all the P. multocida DNAs, but resistance to PstI was confined to LFB3. Plasmid pPM1 treated with PstI methylase was able to transform LFB3 at an increased frequency compared to unmethylated DNA, suggesting that LFB3 has a restriction system which cleaves at or near PstI sites.
Insights
Antibiotic resistance plasmids in Pasteurella multocida were studied. A specific plasmid, pPM1, showed low transfer into a toxigenic strain, LFB3, but high transfer after recovery, indicating a strain-specific restriction system.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Naturally occurring antibiotic resistance plasmids are significant in bacterial evolution.
- Pasteurella multocida is an important animal pathogen.
- Understanding plasmid transfer mechanisms is crucial for controlling antibiotic resistance.
Purpose of the Study:
- To investigate the transfer of antibiotic resistance plasmids among Pasteurella multocida strains.
- To characterize the interaction of plasmid pPM1 with the toxigenic P. multocida LFB3 strain.
- To identify potential restriction-modification systems in P. multocida.
Main Methods:
- Isolation of antibiotic resistance plasmids from Pasteurella multocida type D.
- Conjugative and electrotransformation experiments to study plasmid transfer.
- DNA digestion analysis using restriction enzymes (PstI and DpnI).
- Plasmid methylation studies.
Main Results:
- Plasmid pPM1 was successfully transferred to Escherichia coli and some P. multocida isolates.
- Transfer of pPM1 into toxigenic P. multocida LFB3 occurred at very low frequency.
- High-frequency transfer of pPM1 to LFB3 was achieved after recovery from electrotransformants.
- Plasmid DNA from LFB3 was resistant to PstI but sensitive to DpnI, suggesting a PstI restriction system in LFB3.
- Methylation of pPM1 with PstI methylase increased transformation frequency into LFB3.
Conclusions:
- The toxigenic Pasteurella multocida LFB3 strain possesses a restriction system targeting PstI sites.
- This restriction system significantly impacts plasmid DNA transformation efficiency.
- Understanding these mechanisms is vital for managing antibiotic resistance in P. multocida.