CHARACTERIZING HOW THE MICROBIOTA AFFECTS LIFE TRAITS OF CAENORHABDITIS ELEGANS

Abstract

In the intestinal tract, the region most densely populated by microbiota in humans, microbes serve an important immune function by protecting epithelial cells from pathogens while providing key metabolites that aid digestion. The disturbance of microbiota homeostasis has been associated with various human disease states such as obesity and diabetes mellitus. Studying host-microbe interactions in mammalian systems is quite complex, so we have turned to an invertebrate model system. The nematode, Caenorhabditis elegans, is a well-characterized model host due to its genetic traceability, natural bacterial diet, ease of culture, and short lifespan. Feeding on different bacterial food sources confers differences in life traits such as nematode development, brood size, lifespan, and metabolic activity. In our study, we characterized the E. coli strain BW25113, a K-12 derivative that serves as the parent strain of the Keio Collection, a genomic library of single-gene deletion mutants. Experiments demonstrated that wildtype BW25113 accelerates egg-laying, shortens lifespan, and more quickly populates the gut of C. elegans when compared to E. coli OP50, the standard laboratory feeding strain for the nematode. Interestingly, UV-killed BW25113 and OP50, which are metabolically inactive, both increase the lifespan of worms compared to their respective live strains. When Keio Collection mutants were assayed for their effects on lifespan extension in C. elegans, Keio mutant strains flgD, cheR, and aroC reported significant lifespan extension. These results suggest that bacterial chemotaxis and motility mechanisms are important in increasing the pathogenicity of the gut microbiota. Additionally, the reduction of bacterial chorismate production causes lifespan extension in C. elegans, which is a result supported by previous research.