On some genetic aspects of phage lambda resistance in E. coli K12

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Bacterial resistance to bacteriophages is a critical factor in microbial ecology and evolution.
• Phage lambda resistance in E. coli K12 has been genetically mapped to specific chromosomal regions.
• Understanding the genetic basis of phage resistance can elucidate bacterial surface protein function.

Purpose of the Study:

• To genetically characterize mutations conferring resistance to phage lambda in E. coli K12.
• To determine the genetic organization and function of genes involved in phage lambda resistance, particularly in the malB region.
• To investigate the regulatory relationship between maltose metabolism genes and phage lambda resistance.

Main Methods:

• Genetic mapping of mutations conferring phage lambda resistance.
• Complementation analysis to determine the number of cistrons and gene function.
• Polarity effects to infer gene organization within operons.
• Analysis of intracistronic complementation to assess protein structure.

Main Results:

• Most phage lambda resistance mutations in E. coli K12 map to the malA and malB genetic regions.
• The lamB gene in the malB region is monocistronic and crucial for lambda receptor synthesis.
• Mutations in a proximal maltose metabolism gene can inactivate lamB by polarity, indicating they are in the same operon.
• Intracistronic complementation suggests the lamB product is an oligomeric protein.
• The malT gene in the malA region is a positive regulatory gene for maltose operons in both malA and malB regions.

Conclusions:

• The lamB gene is monocistronic and essential for phage lambda receptor synthesis in E. coli K12.
• The lamB gene and a proximal maltose metabolism gene are part of the same operon, regulated by malT.
• The phage lambda resistance phenotype is linked to maltose metabolism regulation in E. coli K12.