Wild Caenorhabditis nematodes have been found in association with a diverse array of pathogenic microbes, including viruses, bacteria, and fungi. In particular, an intracellular parasite called microsporidia has been commonly found in C. elegans and C. briggsae nematodes isolated from the wild. Microsporidia comprise a highly diverged phylum of obligate intracellular, eukaryotic parasites, which are distantly related to fungi, with over 1,400 species identified that can infect a wide variety of animal species. Here, we characterize infection by three related species of microsporidia, all in the genus Nematocida. Nematocida parisii infects and carries out its entire replicative lifecycle in the intestine of C. elegans. Using transcriptional analysis, we recently identified a robust early C. elegans response to N. parisii infection (Bakowski et al, PLoS Pathogens 2014). This early response may promote defense against N. parisii infection, as the
jy1 C. elegans mutant, which has constitutive expression of these infection response genes, has a 5-8 fold decrease in pathogen load compared to N2. Strikingly, another species of microsporidia, Nematocida
sp1, fails to strongly induce this early transcriptional response upon infection. N.
sp1 also infects the intestine of C. elegans, and is the most closely related species to N. parisii identified to date. We found that N.
sp1 showed a 10-25-fold reduction in induction of these early microsporidia induced genes compared to N. parisii at the same dose. Intriguingly, N.
sp1 was less able than N. parisii to infect the C. elegans
jy1 mutant, where these early induced genes are constitutively overexpressed.Finally, we describe the isolation of a new species of microsporidia found in the epidermis of wild C. elegans. Phylogenetic analysis based on 18s rDNA sequencing places this new species in the Nematocida genus. We have observed all the stages of the microsporidia parasite lifecycle of this new species in the host epidermis. Altogether, we describe distinct characteristics of three related species of Nematocida microsporidia that infect wild C. elegans, and we plan to characterize the mechanisms that these species have evolved to carve out their niches in the nematode. .