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Organization and nucleotide sequences of two lactococcal bacteriocin operons
M J van Belkum1, B J Hayema, R E Jeeninga
1Department of Genetics, University of Groningen, Haren, The Netherlands.
Applied and Environmental Microbiology
|February 1, 1991
Summary
Researchers sequenced two plasmid regions from Lactococcus lactis subsp. cremoris 9B4, identifying genes for bacteriocin production and immunity. Both regions showed identical upstream sequences, suggesting a common regulatory mechanism for bacteriocin operons.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Lactococcus lactis subsp. cremoris 9B4 produces bacteriocins, which are antimicrobial peptides.
- Plasmid-encoded genes often confer bacteriocin production and immunity.
- Understanding these genetic elements is crucial for applications in food preservation and probiotics.
Purpose of the Study:
- To sequence and analyze two distinct regions of the Lactococcus lactis subsp. cremoris 9B4 plasmid p9B4-6.
- To identify the open reading frames (ORFs) responsible for bacteriocin production and immunity.
- To investigate the genetic organization and regulation of these bacteriocin operons.
Main Methods:
- DNA sequencing of plasmid fragments.
- Deletion and frameshift mutation analyses to determine gene function.
- Primer extension analysis to identify promoter regions.
Main Results:
- Two functional regions on plasmid p9B4-6 were identified, each encoding bacteriocin production and immunity.
- A 1.8-kb fragment contained a three-ORF operon (bacteriocin and immunity genes); a 1.3-kb fragment contained a two-ORF operon (bacteriocin and immunity genes).
- The nucleotide sequences upstream of the first ORFs and the initial 20 bp of the first ORFs were identical in both operons, indicating conserved regulatory elements.
Conclusions:
- The plasmid p9B4-6 carries distinct genetic elements for bacteriocin production and self-immunity.
- A conserved promoter region likely regulates both bacteriocin operons in Lactococcus lactis.
- These findings provide insights into the genetic basis of bacteriocin systems in lactic acid bacteria.