An accessory role for Escherichia coli integration host factor: characterization of a lambda mutant dependent upon...

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Bacteriophage lambda typically grows on Escherichia coli, utilizing integration host factor (IHF) for site-specific recombination and gene regulation.
• E. coli strains lacking IHF normally support lytic growth of wild-type lambda.

Purpose of the Study:

• To characterize a mutant bacteriophage lambda (lambda cos154) that exhibits defective growth in IHF-deficient E. coli.
• To identify the genetic basis and functional consequences of the mutation affecting lambda growth in the absence of IHF.

Main Methods:

• Characterization of bacteriophage lambda mutant growth in specific E. coli strains.
• Genetic analysis to identify the mutation responsible for altered growth phenotype.
• Investigation of the mutation's effect on bacteriophage DNA packaging.

Main Results:

• A novel lambda mutant, lambda cos154, was identified as defective for growth in IHF-deficient E. coli.
• The mutation is cis-dominant, located near the left cohesive end, and involves a single base pair change within a dyad symmetry region.
• This mutation was shown to prevent essential bacteriophage DNA packaging.

Conclusions:

• The identified mutation in lambda cos154 disrupts a critical site involved in bacteriophage DNA packaging.
• This site may function by binding either an E. coli accessory protein or the phage terminase, particularly when IHF is absent.