Chromosome rearrangements induced by recombinant coliphage lambda placMu.

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Genetics

Background:

• Operon fusions to lacZ are standard tools for studying bacterial gene expression in vivo.
• Phage derivatives like lambda placMu53 and Mud-1 are commonly used for constructing these fusions.
• These phage derivatives contain a portion of the trp operon, which can interact with the chromosomal trp operon.

Purpose of the Study:

• To investigate the high-frequency recombination events occurring between phage-integrated trp DNA and the chromosomal trp operon.
• To understand the mechanism leading to chromosomal inversions and lacZ fusion to the trp promoter.
• To highlight the implications of these rearrangements for genetic studies and propose solutions.

Main Methods:

• Construction of operon fusions using lambda placMu53 or Mud-1 phage derivatives.
• Integration of these derivatives into the bacterial chromosome.
• Analysis of recombination events and resulting chromosomal rearrangements.
• Characterization of lacZ operon fusions and their transcriptional direction.

Main Results:

• High-frequency recombination between integrated trp DNA and the chromosomal trp operon was observed.
• This recombination leads to chromosomal inversions, fusing lacZ to the trp promoter.
• Large chromosomal segments can be inverted, potentially complicating the isolation of regulatory mutations.
• The phenomenon offers a method for isolating defined chromosomal inversions.

Conclusions:

• Unintended chromosomal inversions are a significant complication when using trp operon-containing phage derivatives for lacZ fusions.
• Awareness and appropriate precautions are necessary to mitigate these rearrangements in genetic studies.
• This recombination event can be harnessed as a tool for generating and studying chromosomal inversions.