[
International Worm Meeting,
2021]
Functional and morphological parallels to the intestines of humans, as well as the variety of microbes that make up its natural microbiome, have led to the emergence of C. elegans as a model system to study host-microbe interactions in vivo. Through ecological sampling, we have identified three bacterial species that bind longitudinally to the intestinal epithelial cells of Caenorhabditis isolates. DIC microscopy imaging reveals these adhering bacteria bind in a hair-like pattern along the intestinal wall. We were interested in whether these bacteria had any effects on host fitness when monocolonized in the C. elegans lumen. Interestingly, we found adherent bacteria 1 (LUAb1), negatively affects the life span and brood size of C. elegans, whereas the two others, adherent bacteria 2 and 3 (LUAb2 and LUAb3), have a neutral effect on C. elegans fitness and are best classified as commensal bacteria. We conducted 16s rRNA sequencing by extracting worm intestines, conducting PCR with universal bacterial primers, and Sanger sequencing of the amplicon. This approach revealed all three bacterial isolates to be novel. LUAb1 and LUAb3 belong to the Enterobacteriaceae family, whereas LUAb2 belongs to the Alphaproteobacterial class. Fluorescence in situ hybridization (FISH) probes were designed to these three bacterial strains to allow for visualization in the intestines. We found LUAb1 colonized nearly 90% of the anterior-posterior intestinal length in more than 90% of the population. Although LUAb2 and LUAb3 colonized the intestines of the worm less than 90% of the intestinal length, the frequency of colonization is the same. Moreover, LUAb3 is the only strain currently culturable in vitro. Whole genome sequence of LUAb3 revealed it is not a new species, but rather a Gram-negative bacterium Lelliottia jeotgali. Absent from the complete L. jeotgali genome sequence, however, was a plasmid encoding a Type IV secretion system, pilins, and adhesins found in LUAb3. We plan to investigate if this plasmid facilitates adherence in the C. elegans lumen. To summarize, we have found three bacterial isolates that exhibit a directional binding phenotype in the intestinal epithelium of C. elegans. We plan to elucidate the host and bacterial receptors that facilitate this adherence mechanism through a forward genetic screen in C. elegans. This research could expand our current understanding of the C. elegans microbiome and inform host-microbe interaction studies in other animals.