Microsporidia are typically found in the intestinal tracts of animals and humans, which are made up of millions of cells, which is why studying their mode of reproduction has been so difficult. Yet it's important. Microsporidia cause diarrhea, an illness called microsporidiosis, and even death in immune-compromised individuals.
In spite of those known widespread medical problems, scientists were uncertain about how these single-celled fungi reproduced in human or animal cells. In a study that employed transparent roundworms, biologists at the University of California San Diego succeeded in directly observing how these microorganisms replicate and spread. And what they saw surprised them.