E. coli K12 inf: a mutant deficient in prophage lambda induction and cell filamentation.

Area of Science:

• Microbiology
• Bacteriology
• Molecular Biology

Background:

• The bacterial mutant inf-3 (lambda) displays non-inducible characteristics and fails to form filaments after thymine starvation.
• Lysogenic induction by ultraviolet light (UV) or tif-1 is not observed in this mutant.

Purpose of the Study:

• To characterize the infA3 mutation in E. coli K12 and its effects on bacterial responses to DNA damage and phage induction.
• To investigate the genetic basis of resistance to UV and thymine starvation in bacterial mutants.

Main Methods:

• Genetic mapping of the infA3 mutation on the E. coli K12 chromosome.
• Phenotypic analysis of bacterial resistance to UV and X-ray irradiation.
• Assessment of phage lambda lysogenic induction, host cell reactivation, and UV-reactivation.
• Evaluation of DNA degradation and synthesis resumption post-UV exposure.
• Analysis of phage reproduction capacity (lambda, T4, T6) and DNA transcription.

Main Results:

• The infA3 mutation confers resistance to UV and X-ray irradiation, unlike other non-inducible mutants.
• The mutant is Rec+ and proficient in host cell reactivation and UV-reactivation of phage lambda.
• Despite increased DNA degradation and delayed DNA synthesis after UV, cell survival is comparable to the parent strain.
• The inf mutant shows resistance to thymine starvation and impaired reproduction of phages lambda, T4, and T6.
• No gross defects in DNA transcription were detected, suggesting a potential subtle alteration in gene expression.

Conclusions:

• The infA3 mutation confers a unique resistance phenotype to DNA-damaging agents and affects phage-host interactions.
• The findings suggest a potential role for the infA gene in regulating DNA replication, cell division, and prophage induction.
• Further investigation into gene expression mechanisms in the inf mutant is warranted to understand its pleiotropic effects.