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An evolutionary relationship between the ColE5-099 and the ColE9-J plasmids revealed by nucleotide sequencing.
M D Curtis1, R James, A Coddington
1Molecular Biology Sector, School of Biological Sciences, University of East Anglia, Norwich, UK.
Journal of General Microbiology
|October 1, 1989
Summary
Researchers sequenced a plasmid fragment encoding colicin E5 immunity and release genes. Colicin E5 shows unique amino acid sequences, suggesting a novel cell-killing mechanism and a close evolutionary link to other E colicins.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- Colicins are bacteriocins produced by Escherichia coli.
- Colicin E5 is a specific type of colicin with a unique mechanism of action.
- Understanding colicin genes and their regulation is crucial for bacterial genetics.
Purpose of the Study:
- To determine the nucleotide sequence of a fragment from the ColE5-099 plasmid.
- To identify genes encoding colicin E5 immunity, colicin release (lys gene), and the colicin E5 structural gene.
- To analyze the evolutionary relationship between ColE5-099 and other E colicin plasmids.
Main Methods:
- DNA sequencing of a 1124 bp plasmid fragment.
- Sequence analysis to identify open reading frames (ORFs).
- Comparison with known E colicin plasmid sequences.
- Subcloning and transposon mutagenesis to confirm gene locations.
Main Results:
- The nucleotide sequence of the 1124 bp fragment was determined.
- ORFs for colicin E5 immunity, lys gene, and the 3' end of the colicin E5 structural gene were identified.
- The carboxy-terminal amino acid sequence of colicin E5 showed no homology to other E colicins.
- A close evolutionary relationship between ColE5-099 and ColE9-J plasmids was suggested.
Conclusions:
- The sequenced fragment contains key genes for colicin E5 production and immunity.
- Colicin E5 likely possesses a distinct mechanism for killing sensitive cells.
- ColE5-099 and ColE9-J plasmids share a common evolutionary origin.