Disrupting Glutamate Metabolism: Exploring the Role of gdhA in E. Coli Growth and Bacteriophage Replication

Abstract

Glutamate metabolism plays a central role in linking carbon and nitrogen utilization in Escherichia coli, yet its contribution to bacteriophage replication remains poorly understood. Bacteriophages are viruses that specifically infect and replicate within bacteria. The enzyme glutamate dehydrogenase (GDH), encoded by ΔgdhA, converts glutamate into α-ketoglutarate, a key TCA cycle intermediate that supports energy production and stress responses. This project aimed to determine how deletion of the ΔgdhA gene affects E. coli growth and T4 bacteriophage infection, and whether disrupting this pathway alters host susceptibility to viral replication. To address this question, we compared the growth of the ΔgdhA knockout strain to its parent strain using OD₆₀₀ growth curves in LB and M9 media. We also performed plaque assays and lysis curves experiments to analyze T4 phage replication across both strains. Our results show that the ΔgdhA knockout grows more slowly than the parent strain, especially in M9 media, suggesting deficient energy metabolism when glutamate cannot be efficiently converted into α-ketoglutarate or reduced availability of glutamate. In the phage experiments, the knockout displayed slower and weaker lysis than the parent strain, indicating reduced susceptibility to T4-induced cell death. Plaque formation with the addition of T4 phage was inconsistent across dilutions but generally showed lower replication in the knockout strain. Together, these findings suggest that GDH activity contributes not only to bacterial growth but also to phage replication. Our future directions will involve repeating the growth and lysis experiments, as well as attempting a two-time point phage titer experiment to strengthen data accuracy, as well as investigating how disruptions to the TCA cycle influence phage infection. Therapies that combine phage treatment with metabolic inhibitors may be developed with an understanding of how bacterial metabolism affects phage susceptibility. Enhancing particular metabolic pathways may increase the susceptibility of resistant bacteria to phage therapy if altering glutamate metabolism decreases phage replication. This is an important factor to consider as antibiotic resistance increases.