Description

Wild nematodes are naturally associated with bacteria in their intestinal tract, making them excellent models for host-microbe interactions. Caenorhabditis elegans are considered an ideal model organism for microbiome research due to similarities between their intestine and polarized intestinal cells in mammals. Additionally, the worms are fully transparent, which is especially beneficial to visualize bacterial adhesion in their intestine. Many adhering bacteria are beneficial to the gut because of their ability to attach to specific cells and help develop host defense. Additionally, they can outcompete with pathogenic microbes to create an ideal niche in the intestine. We have identified wild nematode isolates from around the world colonized with bacteria that directionally adhere to the intestinal epithelium. One of these adhering bacteria is Lelliottia jeotgali. To better understand the effect of L. jeotgali on host fitness, we performed reproductive lifespan and brood size assays. We found that there was no effect on C. elegans fitness when animals were monocolonized with L. jeotgali when compared to the same C. elegans strain without bacteria colonization. This data suggests that L. jeotgali is a commensal-like bacteria of the microbiome. Additionally, we conducted a proliferation assay to observe how the bacteria grow and persist in the intestine. We observed that after worms are briefly exposed to L. jeotgali, the number of bacteria increase over time, suggesting that it can proliferate in the lumen. We believe that the capacity of L. jeotgali to adhere to the C. elegans intestine is due to the presence of a novel plasmid that contains genes encoding for fimbriae, adhesions, and a Type IV secretion system. We cured L. jeotgali such that it does not contain this plasmid and we found that it does not have any adhering properties. Our next step is to see if this plasmid is sufficient to confer binding by mating L. jeotgali with the plasmid to a related non-adherent bacterial strain, Lelliottia amnigena, and seeing if this bacterial species gains adherence in vivo. Altogether, this research presents an opportunity to better understand adhering commensal microbiome bacteria in the context of a whole intact animal.