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Characterization of Lactococcus lactis UV-sensitive mutants obtained by ISS1 transposition
P Duwat1, A Cochu, S D Ehrlich
1Génétique Microbienne, Institut National de la Recherche Agronomique,Jouy en Josas, France. duwat@biotec.jouy.inra.fr
Journal of Bacteriology
|July 1, 1997
Summary
This study identifies DNA repair genes in Lactococcus lactis, revealing that UV resistance depends on both DNA repair mechanisms and cell envelope factors. This research highlights species-specific differences in bacterial stress responses.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- DNA repair mechanisms are crucial for bacterial survival under mutagenic stress.
- While extensively studied in Escherichia coli, DNA repair pathways in other bacteria, like Lactococcus lactis, remain less understood.
- Environmental conditions can influence bacterial DNA repair strategies.
Purpose of the Study:
- To identify and characterize genes involved in DNA repair and resistance to mutagenic agents in Lactococcus lactis.
- To investigate the specific roles of identified genes in DNA repair and homologous recombination.
- To explore potential links between cell envelope composition and resistance to mutagenic stress.
Main Methods:
- Mutagenesis of Lactococcus lactis MG1363 using transposition vector pG+host9::ISS1.
- Isolation and characterization of mutants sensitive to mitomycin and UV radiation.
- DNA sequence analysis to identify insertion loci and affected genes.
- Phenotypic analysis of selected mutants, including UV sensitivity and homologous recombination assays.
Main Results:
- Eleven distinct loci were identified, with mutations in genes related to DNA metabolism (polA, hexB, deoB), cell envelope formation (gerC, dltD), and various metabolic pathways (arcD, bglA, gidA, hgrP, metB, proA).
- Seven mutants were further characterized, confirming UV sensitivity at optimal growth temperature (30°C).
- Three mutants (gidA, polA, and uvs-75) exhibited defects in homologous recombination capacity.
Conclusions:
- UV resistance in Lactococcus lactis is partly mediated by DNA repair genes.
- Cell envelope composition may play a significant role in bacterial resistance to mutagenic stress.
- This study reveals species-specific variations in DNA repair and stress response pathways compared to E. coli.