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Bacteriophage Mu sites and functions involved in the inhibition of lambda::mini-Mu growth
A C Glasgow1, J L Miller, M M Howe
1Department of Bacteriology, University of Wisconsin, Madison 53706.
Abstract:
To better understand the nature of the mini-Mu-directed process which results in inhibition of lambda::mini-Mu growth we characterized spontaneous deletion mutants of the lambda::mini-Mu phage. On the basis of analysis of the deletion endpoints, mini-Mu replication functions, and integration and inhibition properties, the lambda::mini-Mu deletion mutants were divided into five classes which define the Mu sites and functions involved in lambda::mini-Mu growth inhibition. Class 1 mutants, which still exhibit lambda::mini-Mu growth inhibition, collectively delete all the Mu late functions encoded by the mini-Mu. Class 2 and 5 mutants, which show cis-dominant defects in inhibition and integration, delete the right and left mini-Mu attachment sites, respectively. Phages of Classes 3 and 4, which delete the Mu B or A and B genes, respectively, show recessive defects in growth inhibition. The properties of these mutants define the Mu replication functions, A and B, and the Mu attachment sites as essential for the inhibition of lambda::mini-Mu growth. The observation that the sites and functions essential for Mu replication also have requisite roles in the inhibition of lambda::mini-Mu growth suggests that inhibition results from mini-Mu-promoted replicative interference of lambda::mini-Mu development.
Insights
This study investigated how mini-Mu phage inhibits lambda::mini-Mu growth by analyzing deletion mutants. Key Mu replication functions and attachment sites are essential for this growth inhibition process.
Area of Science:
- Molecular Biology
- Virology
- Bacteriophage Genetics
Background:
- The mini-Mu phage is known to inhibit the growth of lambda::mini-Mu phage.
- The precise mechanisms underlying this inhibition are not fully understood.
Purpose of the Study:
- To elucidate the nature of the mini-Mu-directed inhibition of lambda::mini-Mu growth.
- To identify the specific Mu sites and functions involved in this process.
Main Methods:
- Characterization of spontaneous deletion mutants of lambda::mini-Mu phage.
- Analysis of deletion endpoints, mini-Mu replication functions, and integration/inhibition properties.
- Classification of mutants into five distinct groups based on their genetic defects.
Main Results:
- Mutants were classified into five groups, defining Mu sites and functions critical for lambda::mini-Mu growth inhibition.
- Class 1 mutants retained inhibition despite deleting all mini-Mu late functions.
- Class 2 and 5 mutants showed cis-dominant defects, deleting right and left mini-Mu attachment sites, respectively.
- Class 3 and 4 mutants exhibited recessive defects, deleting Mu B or A and B genes, respectively.
Conclusions:
- Mu replication functions (A and B) and Mu attachment sites are essential for inhibiting lambda::mini-Mu growth.
- The findings suggest that inhibition arises from mini-Mu-promoted replicative interference during lambda::mini-Mu development.