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Theta replication of the lactococcal plasmid pWVO2
R Kiewiet1, S Bron, K de Jonge
1Department of Genetics, Centre of Biological Sciences, Haren, The Netherlands.
Molecular Microbiology
|October 1, 1993
Summary
The pWVO2 plasmid from Lactococcus lactis replicates using a theta mechanism, not rolling-circle. This discovery opens possibilities for developing stable food-grade cloning vectors in L. lactis.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Lactococcus lactis is a key bacterium in dairy fermentation.
- Plasmids play crucial roles in bacterial adaptation and genetic exchange.
- Understanding plasmid replication mechanisms is vital for genetic engineering.
Purpose of the Study:
- To investigate the replication mechanism of the narrow-host-range plasmid pWVO2 from Lactococcus lactis.
- To determine if pWVO2 replicates via a rolling-circle or theta mechanism.
- To explore the potential of pWVO2 derivatives as food-grade cloning vectors.
Main Methods:
- Plasmid DNA analysis in Lactococcus lactis.
- Sequence analysis of the pWVO2 plasmid.
- 2-D agarose gel electrophoresis to identify replication intermediates.
Main Results:
- pWVO2 does not replicate via a rolling-circle mechanism in L. lactis.
- Evidence from 2-D gel electrophoresis confirms theta replication for pWVO2.
- The minimal replicon of pWVO2 shares features with other theta-type plasmids, including iterons.
- Derivatives of pWVO2 demonstrated stable maintenance in L. lactis.
Conclusions:
- pWVO2 is the first identified theta-replicating plasmid in lactococci.
- The structural organization of pWVO2's replication machinery resembles theta-type plasmids found in E. coli.
- pWVO2 derivatives are promising candidates for developing stable, food-grade cloning vectors for Lactococcus lactis.