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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
Published on: May 2, 2018
DNA sequence analysis of three Lactococcus lactis plasmids encoding phage resistance mechanisms
1Department of Biochemistry and Microbiology, Faculté des Sciences et de Génie, Faculté de Médecine Dentaire, Université Laval, Quebec, Canada.
Journal of Dairy Science
|July 27, 2001
Summary
Three Lactococcus lactis plasmids (pSRQ700, pSRQ800, pSRQ900) conferring anti-phage resistance were sequenced. Their genetic organization and safety for food applications were confirmed, indicating suitability for dairy fermentation.
Area of Science:
- Microbiology
- Molecular Biology
- Food Science
Background:
- Lactococcus lactis is crucial for dairy fermentation.
- Phage contamination poses a significant threat to industrial dairy production.
- Plasmids conferring anti-phage resistance are valuable tools for protecting starter cultures.
Purpose of the Study:
- To determine the complete DNA sequences of three Lactococcus lactis plasmids (pSRQ700, pSRQ800, pSRQ900).
- To analyze the genetic organization and identify genes responsible for anti-phage mechanisms.
- To assess the safety and suitability of these plasmids for food-grade applications in dairy fermentation.
Main Methods:
- Whole-genome sequencing of plasmids pSRQ700, pSRQ800, and pSRQ900.
- Bioinformatic analysis of plasmid DNA sequences to identify coding regions and genetic elements.
- Functional analysis of HsdS subunits in L. lactis IL1403 to assess phage resistance.
- Evaluation of plasmid features for food-grade suitability.
Main Results:
- Complete sequences of pSRQ700 (7784 bp), pSRQ800 (7858 bp), and pSRQ900 (10,836 bp) were determined, revealing similar genetic organization with a common theta-type replicon.
- Genes for anti-phage mechanisms (LlaDCHI, AbiK, AbiQ) and type I restriction/modification system subunits (HsdS) were identified.
- HsdS subunits from pSRQ800 and pSRQ900 conferred weak resistance against phage P008 in L. lactis IL1403, complementing the host system.
- Plasmids contain replication modules, potential transfer origins, tyrosine recombinases, and bacteriocin-related genes (pSRQ900), with no detected anti-lactococcal activity.
Conclusions:
- The sequenced plasmids possess genetic elements conferring phage resistance and potentially other functions.
- The identified HsdS subunits can enhance phage resistance in L. lactis strains.
- These plasmids are deemed safe and suitable for food-grade applications in the dairy industry.
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