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. 2017 Jun 1;6:e26243. doi: 10.7554/eLife.26243

Figure 1. C. elegans do not eat heat-killed bacteria without interacting with live bacteria.

(A) Microscope images and bar graph showing that worms fed heat-killed OP50 (HK-OP50 or HK) arrested at L1-L2 stage three days after hatching. (B) Schematic drawing and quantitative data of the food dwelling assay. Circles indicate the food spot for live (green) and HK-OP50 (red) bacteria, respectively. The animals were scored 24 hr after L1 worms were placed on the food spot. Data are represented as mean ±SD. (C) Schematic drawing, microscopic images and quantitative data of the food choice assay. Eggs were place in the center spot (origin). Live (green) and heat-killed (red) bacteria were placed on opposite sides of the plate. The percentage of worms on each spot was calculated at the indicated time. Worms moved to heat-killed bacteria and consumed it after 4 days when live food was totally consumed. Data are represented as mean ±SEM. (D) An assay for the effect of a small amount of live, non-edible bacteria on the growth of animals fed heat-killed bacteria. The colored diagrams show the feeding conditions. Percentage of animals that grew to L3-adult stages is indicated below each diagram. The combination of HK-OP50 and small amount live SS, neither of which alone can support growth, could support food uptake and growth. The control (4th column) suggests that only live SS can promote worms to consume HK-OP50. For bar graphs, number of worms scored is indicated in each bar. All data are representative of at least three independent experiments.

DOI: http://dx.doi.org/10.7554/eLife.26243.003

Figure 1—source data 1. Numerical data of Figure 1A–1D and Figure 1—figure supplement 1C.
DOI: http://dx.doi.org/10.7554/eLife.26243.004
elife-26243-fig1-data1.xlsx (16KB, xlsx)
DOI: 10.7554/eLife.26243.004

Figure 1.

Figure 1—figure supplement 1. Impact of interaction with live bacteria on the ability of C. elegans to consume heat-killed bacteria.

Figure 1—figure supplement 1.

(A) Worms on heat-killed OP50 (growth for 30 days) can be recovered once they eat live OP50. Once live-OP50 (yellow arrow and dotted line) was added to worms (red arrow) grown on HK-OP50 plate for 30 days, they recovered to adults with viable progeny. This result suggests that nutrient deficiency in HK-OP50 induced a protective response from the worms similar to starvation response. (B) Representative images of animals in the assay described in Figure 1D. Only under the HK-OP50+ live SS condition, worms were able to consume all heat-killed bacteria and grow. (C) Cartoon illustrations, microscopic images and quantitative data showing that live bacteria do not influence the usability of heat-killed bacteria through odorants. In the middle cartoon, two petri dishes are stacked with top (opening) facing each other so that the worms/food on the agar pads are exposed to common air space, >100 worms were scored for each testing condition. S.S.= Staphylococcus saprophyticus..
DOI: http://dx.doi.org/10.7554/eLife.26243.005