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A genetic study of Escherichia coli strains carrying Mu-lambda-Mu structures
Abstract:
We have studied the interaction of bacteriophages Mu and lambda after their simultaneous induction and the influence of lambda on Mu-dependent mobilization of the E. coli chromosome by the RP4 plasmid. Heterolysogenic E. coli strains carrying Mu-lambda-Mu structures were constructed (Faelen et al. 1975). The Mu and lambda prophages are linked in such structures, and the functions of some lambda genes are disturbed depending on the integration site. A study of the inhibition of Mu growth by lambda after their simultaneous induction was performed and the region of the lambda genome (R-H) which contains the gene(s) responsible for the inhibitory effect of lambda on Mu was identified. The efficiency of Mu-dependent mobilization of the bacterial chromosome by RP4 is shown to be an order of magnitude lower in strains with unlinked Mu and lambda and an order of magnitude higher in strains with some permutations of the lambda prophage than in the control Mu-monolysogenic E. coli strain. Thus the effect of Mu on mobilization depends on the localization of the lambda prophage and on the functioning of its genome within a Mu-lambda-Mu structure. It is presumed that the mobilization of the bacterial chromosome is stimulated by effective replication of the Mu genome starting from the ori site (origin of replication) of the lambda prophage within the Mu-lambda-Mu structure. We propose a model to explain the interaction of Mu and lambda in E. coli strains carrying Mu-lambda-Mu structures.
Insights
Bacteriophage lambda inhibits bacteriophage Mu growth and influences Mu-dependent E. coli chromosome mobilization. Lambda
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Bacteriophages Mu and lambda are viruses that infect bacteria.
- Their interactions can affect bacterial processes like chromosome mobilization.
- Understanding these interactions is crucial for genetic engineering and phage therapy.
Purpose of the Study:
- To investigate the interaction between bacteriophages Mu and lambda.
- To determine lambda's influence on Mu-mediated E. coli chromosome mobilization.
- To identify the specific lambda genome region responsible for inhibiting Mu growth.
Main Methods:
- Construction of heterolysogenic E. coli strains with Mu-lambda-Mu structures.
- Simultaneous induction of Mu and lambda phages.
- Analysis of Mu growth inhibition by lambda.
- Quantification of Mu-dependent chromosome mobilization by RP4 plasmid.
Main Results:
- Identified the R-H region of the lambda genome responsible for inhibiting Mu growth.
- Mu-dependent chromosome mobilization was significantly reduced in strains with unlinked Mu and lambda.
- Mobilization efficiency increased in strains with specific lambda prophage permutations within Mu-lambda-Mu structures.
- Lambda's influence on Mu-dependent mobilization is dependent on prophage localization and lambda gene function.
Conclusions:
- Lambda's interaction with Mu within Mu-lambda-Mu structures modulates E. coli chromosome mobilization.
- Effective replication of the Mu genome, potentially initiated from the lambda prophage's origin of replication, stimulates bacterial chromosome mobilization.
- A model is proposed to explain the complex interplay between Mu and lambda in E. coli.