Host metabolism is profoundly altered during bacterial infection, both as a consequence of immune activation and secondary to virulence strategies of invading pathogens. As a result, the metabolic pathways that regulate nutrient acquisition, energy storage, and resource allocation in host cells must adapt to pathogen stress in order to meet the physiological demands of the host during infection. However, the specific alterations in host metabolism that occur during bacterial infection are

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... nging to decipher, owing to physiological disruption in multiple organ systems that occur during infection and complex metabolic interactions between the host and the pathogen. In this regard, the nematode Caenorhabditis elegans has emerged as a useful starting point to characterize fundamental principles of immunometabolism. For nematodes, bacteria are both a source of food and agents of disease. As such, C. elegans has evolved innate immune defenses coordinated by intestinal epithelial cells, which promote survival during infection by ingested pathogens. Studies of pathogen infection in C. elegans can therefore be used to define changes in host metabolism specifically associated with infection by pathogenic bacteria in the intestine. Here, we discuss 5 concepts that have emerged in studies of metabolic and immune interactions in C. elegans (Fig 1) . The major emerging theme is that the immune response and the ability to survive pathogen infection is heavily influenced by pathogen-induced changes in host metabolism.