Discovery of a Natural Microsporidian Pathogen with a Broad Tissue Tropism in Caenorhabditis elegans
(a) C. elegans intestinal GFP expression strain ERT413 at 1 dpi stained with N. displodere rRNA FISH. Sporoplasms are seen inside and outside of the GFP-labeled intestine, in close proximity to the intestine, but never anterior to the posterior bulb (PB). Scale bar is 10 μm. (b) Exterior polar tubes associated with a spore were measured for N. displodere and N. parisii small spores. Each data point represents a measured polar tube, with the line and error bars showing the mean and SD of n = 40 for N. displodere and n = 41 for N. parisii. Note polar tubes of N. displodere and N. parisii were measured with separate techniques on separate occasions. The image (right) shows an N. displodere spore stained by Calcofluor white (CFW) with the associated polar tube stained by Concanavalin A-rhodamine (ConA). Scale bar is 10 μm. (c) The widths of GFP-labeled intestine from L3 larvae and young adults were measured in the anterior and posterior regions of the animal and halved to estimate the distance from the lumen to the basal lateral side of the intestine. The mean and SD from n = 14 L3 animals and n = 8 young adults are indicated (***p = 0.0002, two-tailed Mann-Whitney test). (d) The tissue distribution of invasion events of N. displodere infection (sporoplasms) was analyzed after 30 minutes of infection in L3 larvae versus young adults, and was calculated in the tissue-specific strains expressing GFP in the intestine (left) and muscle (right). Invasion events were calculated as the percent of FISH-stained sporoplams occurring outside of the GFP-expressing intestine (left) or inside the GFP-expressing muscle (right) compared to the total number of events throughout the animals. Data are represented as mean with SD of four replicates across two experiments, with a total of 25 animals counted for each replicate (*p = 0.0286, two-tailed Mann-Whitney test).