What is it about?
Salmonella can survive and multiply inside macrophages, immune cells that normally destroy invading microbes. The bacterium is thought to depend on specialized molecular systems that manipulate the host cell and create a suitable place for growth. By following individual infected macrophages over time, we found that the nutrients available inside each cell strongly influence whether Salmonella multiplies. Providing certain nutrients, particularly glycerol or galactose, increased bacterial growth. Under these favourable conditions, some bacteria could even multiply without their two major secretion systems, although only in a subset of cells.
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Why is it important?
These findings show that bacterial virulence depends not only on classical virulence factors but also on the nutritional environment provided by the infected cell. Access to suitable nutrients could partially compensate for the absence of important Salmonella secretion systems under laboratory conditions. The study also reveals that macrophages are not metabolically identical: some cells take up and provide more nutrients than others and are therefore more permissive to bacterial replication. This helps explain why genetically identical bacteria can have very different outcomes in different infected cells and highlights host metabolism as a potential target for limiting intracellular infections.
Perspectives
What I find particularly important is that this study changes how we think about the relationship between metabolism and bacterial virulence. Virulence factors do not act in isolation, their importance depends on the environment encountered by the bacterium inside each host cell. Our single-cell approach allowed us to detect bacterial replication in a small subgroup of macrophages that would probably have been missed using conventional population-level measurements. The work now raises important questions about whether changes in nutrient availability during disease, ageing or metabolic disorders can create particularly permissive cellular environments for infection, and whether restricting bacterial access to host nutrients could complement conventional antimicrobial treatments.
Pedro Escoll
Institut Pasteur
Read the Original
This page is a summary of: Provision of preferred nutrients to macrophages promotes Salmonella intracellular replication without relying on Type III secretion systems, PLoS Pathogens, July 2026, PLOS,
DOI: 10.1371/journal.ppat.1014348.
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