Investigating the Role of metR on E. coli Growth and Viral Replication

Abstract

Understanding how bacterial metabolic pathways influence viral infections is fundamental to host-pathogen biology. In Escherichia coli, the transcription factor metR regulates genes required for methionine biosynthesis, an essential pathway for protein synthesis, methylation, and cellular metabolism. Although metR has been studied in relation to how it induces methionine production, it has not been studied whether it is needed for methionine production. This study investigates how deleting metR affects E. coli growth and susceptibility to T4 and T2 bacteriophages. Wild-type E. coli and ΔmetR knockout strains were grown in nutrient-rich LB and nutrient-limited M9 minimal media, and growth was monitored by OD600 measurements. Phage replication was quantified using standard plaque assays, two-point tier measurements, and lysis curves. Additional experiments assessed whether providing exogenous methionine could rescue knockout growth. Across media types, the ΔmetR strain exhibited consistently reduced growth compared to the wild type, with the largest impairment in methionine-deficient M9 minimal media. Upon introducing the T4 bacteriophage, the ΔmetR strain showed increased lysis relative to the parent strain, demonstrating heightened susceptibility to viral replication. Plaque assays with T2 bacteriophage revealed significantly lower infectious particle counts in the knockout strain, indicating reduced phage propagation efficiency. Two-point tier assays confirmed this trend, with the ΔmetR mutant producing fewer virions at both early and late time points. Together, these findings suggest that metR contributes to bacterial growth and to supporting efficient phage replication. Our inconsistent results pose a need for further experiments for better clarity. This work provides insight into how bacterial metabolic regulation intersects with viral infection dynamics. Future studies will focus on introducing methionine back into the knockout phenotype in different dilutions and identifying specific metabolic pathways altered by the ΔmetR deletion that influence phage productivity.