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Genomic organization of Lactococci
B E Davidson1, N Kordias, N Baseggio
1Russell Grimwade School of Biochemistry, University of Melbourne, Parkville, Victoria, Australia.
Developments in Biological Standardization
|January 1, 1995
Summary
The Lactococcus lactis genome exhibits significant plasticity, with extensive chromosomal rearrangements observed across different strains and under laboratory conditions. This genetic flexibility impacts its structure and evolution.
Area of Science:
- Microbiology
- Genomics
- Bacteriology
Background:
- The genus Lactococcus includes four species, with Lactococcus lactis being the most extensively studied.
- Lactococcus lactis possesses an A+T-rich genome comprising a circular chromosome (2.0–2.7 Mbp), numerous plasmids, and often prophages.
- Insertion sequence elements are prevalent in both chromosomal and plasmid DNA, alongside a described 68 kbp conjugative transposon.
Purpose of the Study:
- To investigate the genomic plasticity and structural variations within Lactococcus lactis strains.
- To understand the extent of chromosomal rearrangements and their potential causes in L. lactis.
Main Methods:
- Comparative genomic mapping of different L. lactis strains.
- Induction of chromosomal rearrangements through laboratory methods, including exposure to lytic phage and mutagens.
Main Results:
- Significant differences in genetic maps were observed between L. lactis subspecies.
- A large inversion (approx. 40% of the chromosome) was identified between L. lactis subsp. cremoris and L. lactis subsp. lactis strains.
- Smaller translocations and inversions were also detected, alongside experimentally induced chromosomal rearrangements.
Conclusions:
- The Lactococcus lactis genome demonstrates remarkable plasticity.
- Chromosomal rearrangements are common in L. lactis, influenced by both intrinsic factors and external stimuli like phage infection and mutagens.
- This genomic flexibility is a key characteristic of L. lactis evolution and adaptation.