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Selection of Escherichia coli K-12 chromosomal mutants that prevent expression of F-plasmid functions
Abstract:
Chromosomal mutants of Escherichia coli deficient in the expression of F-plasmid functions were selected by mutagenizing F- cells, introducing an F' plasmid into the mutagenized cells by conjugation, and identifying transconjugants resistant to the donor-specific bacteriophage Q beta by a simple spray test. All but 1 of 25 mutants were defective in an extracellular stage of Q beta infection, suggesting that they fail to elaborate F-pili. At least six of these were also deficient as deoxyribonucleic acid donors. More than half of the mutants appear to be altered in peviously undetected chromosomal genes required for the expression of F-related cellular functions.
Insights
Researchers identified new Escherichia coli chromosomal genes essential for F-plasmid functions. These genes are crucial for F-pili elaboration and deoxyribonucleic acid transfer, impacting bacterial conjugation.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- The F-plasmid facilitates bacterial conjugation in Escherichia coli, a process vital for genetic exchange.
- Expression of F-plasmid functions, including F-pili formation, is essential for initiating cell-to-cell contact during conjugation.
Purpose of the Study:
- To identify and characterize chromosomal genes in Escherichia coli that regulate the expression of F-plasmid functions.
- To investigate the role of these newly identified genes in F-pili elaboration and deoxyribonucleic acid (DNA) transfer.
Main Methods:
- Escherichia coli F- cells were mutagenized and subsequently transformed with an F' plasmid.
- Transconjugants were screened for resistance to bacteriophage Q beta, a process dependent on F-pili.
- Mutants defective in phage resistance were further analyzed for their ability to act as DNA donors.
Main Results:
- Twenty-five chromosomal mutants deficient in F-plasmid functions were isolated.
- Twenty-four of these mutants exhibited defects in an extracellular stage of Q beta infection, indicating a failure in F-pili elaboration.
- At least six mutants were also deficient in deoxyribonucleic acid (DNA) transfer, suggesting a role in conjugation.
Conclusions:
- More than half of the isolated mutants revealed previously undetected chromosomal genes required for F-related cellular functions.
- These findings highlight novel genetic elements on the Escherichia coli chromosome that are critical for the regulation of plasmid-mediated conjugation.