Introducing the Oral Microbiome Into the Model Organism C. elegans

Objectives: The oral microbiome varies greatly among humans and its symbiotic role in human health is poorly understood. Pursuit of this topic depends on identifying a suitable model for analyzing the oral microbiome in the absence of the gut microbiome. In this study we sought to determine if multispecies colonization of the C. elegans intestine with oral bacteria can be established.
Methods: Dorsal tongue scrapings from three healthy individuals were cultured on supplemented chocolate agar and 10 C. elegans worms were transferred to each plate. Worms were allowed to propagate for one week, washed with antibiotics, and transferred to LB agar for two days. DNA from tongue samples, culture plates, and washed worms on LB agar were extracted with MoBio Power Soil DNA isolation kit, and 16S rDNA sequencing was done by LC Biosciences. Bacterial community analysis was done using CLC Genomics Workbench v10. Significant differences between groups were determined by PERMANOVA and differential abundance analysis. Bacterial colonization of the intestine was assessed using confocal microscopy.
Results: C. elegans was able to survive and propagate on a community of oral bacteria; bacteria were visible in the intestine, and viable bacteria were cultured from washed worms. Comparing the initial oral inoculum to cultured bacteria, there was a significant loss of diversity, with observed Operational Taxonomic Units (OTUS) of 100 reduced to an average of 28 after culture. There was not a significant loss of alpha diversity from the culture plate to the worm intestines, as the average observed OTUs in the worms after 2 days on LB agar was 30. The predominant oral organisms colonizing the worms were members of the genera Neisseria, Granulicatella, Streptococcos, and Rothia.
Conclusions: These studies signify C. elegans’ potential usefulness in exploring the role of the oral microbiome as a symbiotic entity.