Genetical and structural analysis of a group of lambda ilv and lambda rho transducing phages

Area of Science:

• Molecular Biology
• Bacteriology
• Genetics

Background:

• Bacteriophage lambda (λ) is a versatile tool for genetic analysis, particularly in E. coli.
• Transducing phages carrying specific bacterial genes are crucial for gene mapping and characterization.
• Understanding the genetic organization and expression of operons like ilv is fundamental in microbial genetics.

Purpose of the Study:

• To genetically and physically characterize eight lambda ilv C transducing phages derived from E. coli K12.
• To determine the location of specific mutations and the molecular weights of gene products.
• To investigate the expression of the ilv G gene and the structure of transducing phages.

Main Methods:

• Genetic analysis of E. coli K12 secondary site lysogens.
• Physical characterization of lambda ilv C transducing phages.
• Electrophoretic analysis of proteins synthesized in UV-irradiated E. coli cells using phage systems.
• Mapping of the ilv O 603 mutation.

Main Results:

• Two phages were found to carry the rho gene and its promoter region, but not the cya gene.
• The ilv O 603 mutation was localized between the ilv G and ilv E genes.
• Molecular weights of 55,000 and 66,000 daltons were assigned to ilv C and ilv D gene products, respectively.
• An ilv G-encoded polypeptide (60,000 daltons) was synthesized from ilv O- phages but not ilv O+ phages.
• One lambda ilv phage exhibited a non-classical transducing phage structure.

Conclusions:

• The study provides detailed genetic and physical characterization of lambda ilv C transducing phages.
• Insights into the expression of the ilv G gene, influenced by upstream regulatory regions, were gained.
• The identification of a non-classical phage structure highlights the diversity in transducing phage formation.