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Persistence of Live Fluorescent E. Coli in the C. Elegans Gut Microbiome

AJAS · 2020

James Eiler · New Hampshire Science Academy

Overview

C. elegans is a common model organism and, because of its transparent anatomy, is easily used for fluorescent imaging. The C. elegans gut microbiome has been found to play an in important role in its behavior and stress resistance. What is not certain and not well examined is whether bacteria inside the C. elegans remain as stable, living colonies for a prolonged period of time after the C. elegans stops consuming the bacteria. To answer this question, a fluorescence assay was performed in which the C. elegans were fed E. coli expressing a teal fluorescent protein. Control C. elegans were fed E. coli of the same strain expressing a red fluorescent protein that does not fluoresce under the light settings used for the teal fluorescent protein. After eating fluorescent bacteria for two days, the worms were observed over a period of three days on plates without bacteria. Images of the C. elegans were recorded on a Nikon SMZ-U microscope with a NIGHTSEA fluorescent light and analyzed for the level of green fluorescence expressed by the teal fluorescent protein. The fluorescence of the day 1 group, morning and afternoon day 2 groups, and morning and afternoon day 3 groups were analyzed and found to be significantly different from each other and the control group of worms not fed teal fluorescent bacteria. The average fluorescence increased from day 1 to day 2 by 0.250 arbitrary fluorescence units (afu), but then decreased between the morning and afternoon of day 2 by 0.562 afu and only decreased by 0.055 afu between the end of day 2 and the end of day 3. All groups had significantly higher fluorescence than controls (p-value<0.05). This suggests that the bacteria maintained a significant presence in the C. elegans gut over the examined period. To confirm the presence of living fluorescent bacteria in the gut after two days on a starvation plate, worms, independent of those photographed, were crushed and plated onto bacterial nutrient plates. Two days after plating the fragmented C. elegans, the plates were examined and fluorescent bacteria colonies were observed. These experiments indicate that that bacteria can survive and maintain a presence in the C. elegans gut for at least two days after the C. elegans stops consuming the bacteria. This prolonged presence indicates that bacteria establish long-term colonies in the C. elegans gut and that this stable microbiome could play a role in the functioning of the organism.

Competition history

  • AJAS 2020 Category not listed

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Source: AAAS Annual Meeting (Confex) / American Junior Academy of Science

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