Adaptive metabolic strategies of intracellular bacterial pathogens

Intracellular bacterial pathogens have evolved sophisticated metabolic strategies to persist and replicate within the hostile intracellular environments of their hosts. By leveraging their metabolic plasticity, these pathogens dynamically modulate host metabolic processes in response to immunological, environmental, and pharmacological stressors. This review examines the diverse metabolic adaptations employed by intracellular pathogens, including nutrient acquisition, modulation of host metabolism, and stress-induced metabolic shifts that contribute to persistence and virulence. Emphasis is placed on how distinct intracellular niches- such as vacuoles and the cytosol- shape pathogen metabolism, and how bipartite metabolic strategies enable pathogens to balance energy production with biosynthetic demands. Species-specific adaptations in representative pathogens, including Listeria monocytogenes, Legionella pneumophila, Shigella flexneri, and Chlamydia trachomatis, are analyzed, with a focus on mechanisms of metabolic reprogramming (the alteration of cellular metabolic pathways in response to environmental cues, such as infection or stress, which allows the pathogen to adapt its metabolic state to support survival, replication, and virulence within the host), stress tolerance (refers to a pathogen's ability to survive and function under harsh environmental conditions, such as oxidative stress, nutrient scarcity, and antimicrobial exposure), and lifecycle transitions (refer to the changes in a pathogen's developmental or replication stages, such as switching from active growth to a dormant or persistent state during infection). Finally, the review considers how these metabolic strategies intersect with antimicrobial resistance and highlights the potential of targeting host-pathogen metabolic interactions for the development of novel interventions, including host-directed therapies (HDTs).