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Functional analysis of the pediocin operon of Pediococcus acidilactici PAC1.0: PedB is the immunity protein and PedD
1Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
Insights
Pediocin PA-1 immunity is conferred by the pedB gene. Pediocin PA-1 transport and processing require the pedC and pedD genes, with PedD processing the precursor.
Area of Science:
- Microbiology
- Molecular Biology
- Bacteriocins
Background:
- The pediocin PA-1 operon in Pediococcus acidilactici PAC1.0 contains four genes: pedA, pedB, pedC, and pedD.
- Transcription yields two overlapping transcripts, suggesting a single promoter upstream of pedA.
Purpose of the Study:
- To elucidate the functions of the genes within the pediocin PA-1 operon.
- To identify the immunity protein and the transport/processing mechanisms for pediocin PA-1.
Main Methods:
- Deletion analysis in Pediococcus pentosaceus.
- Gene overexpression studies.
- Activity assays in Escherichia coli.
Main Results:
- PedB was identified as the pediocin PA-1 immunity protein.
- Both pedC and pedD are essential for extracellular pediocin PA-1 secretion.
- PedD possesses N-terminal domains conserved with bacteriocin ABC-transporters and is responsible for prepediocin processing.
Conclusions:
- PedB confers immunity to pediocin PA-1.
- PedC and PedD are crucial for pediocin PA-1 transport.
- PedD mediates the processing of prepediocin, enabling its maturation.
Abstract:
The bacteriocin pediocin PA-1 operon of Pediococcus acidilactici PAC1.0 encompasses four genes: pedA, pedB, pedC and pedD. Transcription of the operon results in the formation of two overlapping transcripts, probably originating from a single promoter upstream of pedA. The major transcript comprises pedA, pedB, and pedC, while a minor transcript encompasses all of these genes and pedD. By deletion analysis and overexpression of pedB in Pediococcus pentosaceus we demonstrate that this gene encodes the pediocin PA-1 immunity protein. Prepediocin is active in Escherichia coli and when pedA was expressed concomitantly with pedD both the precursor and the mature form of pediocin were observed intracellularly. Extracellular pediocin was only detected if both pedC and pedD were present. The N-terminal domains of PedD and a subgroup of bacteriocin ABC-transporters are conserved. Expression of only this domain of PedD in cells producing prepediocin was sufficient for prepediocin processing. From these results we conclude that both PedC and PedD are essential for pediocin transport, and that PedD is capable of processing prepediocin.