Abstract
Molecular pathways involved in dauer formation, an alternate larval stage that allows Caenorhabditis elegans to survive adverse environmental conditions during development, also modulate longevity and metabolism. The decision to proceed with reproductive development or undergo diapause depends on food abundance, population density, and temperature. In recent years, the chemical identities of pheromone signals that modulate dauer entry have been characterized. However, signals derived from bacteria, the major source of nutrients for C. elegans, remain poorly characterized. To systematically identify bacterial components that influence dauer formation and aging in C. elegans, we utilized the individual gene deletion mutants in E. coli (K12). We identified 56 diverse E. coli deletion mutants that enhance dauer formation in an insulin-like receptor mutant (daf-2) background. We describe the mechanism of action of a bacterial mutant cyaA, that is defective in the production of cyclic AMP, which extends lifespan and enhances dauer formation through the modulation of TGF-β (daf-7) signaling in C. elegans. Our results demonstrate the importance of bacterial components in influencing developmental decisions and lifespan in C. elegans. Furthermore, we demonstrate that C. elegans is a useful model to study bacterial-host interactions.
Highlights
Dauer formation provides an easy to assess, binary readout of the type of food signals emanating from bacteria
To systematically study bacterial products that could act as food signals in C. elegans, we fed worms with bacterial strains from the E. coli Keio knockout library
We have screened for bacterial mutants that regulate dauer formation in C. elegans to understand the role of bacterial genes in modulating nutrient sensing pathways
Summary
Dauer formation provides an easy to assess, binary readout of the type of food signals emanating from bacteria. We demonstrate how multiple individual gene knockouts in E. coli can influence development and survival in C. elegans. Through a systematic screen of ~4000 single gene knockout E. coli strains, we identified 56 E. coli mutants that enhanced dauer formation in a C. elegans insulin-like receptor mutant, daf-2, some of which extended adult lifespan in control worms. One of the largest lifespan extensions was observed by feeding the bacterial mutant, cyaA (adenylate cyclase). We identify that cyaA influences TGF-βsignaling to modulate dauer formation and lifespan. Our results demonstrate that the combination of bacterial and worm genetics can be a powerful tool to study bacterial-host interactions that influence nutrient signaling pathways and organismal physiology that may be relevant for host-microbiome interactions in other species
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