Emerging, Uncommon, and Non-model Organisms

Blog series organized by Eric Peterman, Michael Onken, Kristen Verhey, and Daniel M. Suter

Lillian Fritz-Laylin, Professor of Biology, University of Massachusetts

Briefly describe the model you use.

We work with two emerging model systems; Naegleria gruberi and chytrid fungi. Naegleria is a fascinating single-celled organism that is usually an amoeba that can crawl at speeds topping 120 microns per minute without any cytoplasmic microtubules. Naegleria responds to stress by differentiating into a swimming flagellate and assembling a complex microtubule cytoskeleton. This transition marked the first documented case of de novo centriole assembly, a feat once considered impossible. We also study various chytrid species. These remarkable fungi begin their development as single cells that crawl using actin and swim using flagella and lack cell walls. As they mature, they grow cell walls, shed their flagella, and adopt a similar appearance to yeast or multicellular fungi. The developmental biology of these microbes makes them incredibly well suited for understanding the diversification and specification of actin and microtubule networks.

Can you give a quick overview of your work and why your model organism is best suited for this work?

My lab is interested in understanding how actin and microtubule networks diversify across evolution and how cells specify individual networks for specific functions. We work with Naegleria and chytrids because they undergo drastic changes in their cytoskeletal networks during development and because they occupy pivotal positions in the eukaryotic tree. Naegleria is across the eukaryotic evolutionary tree from animals and yeast and therefore can tell us a lot about the last common eukaryotic ancestor, while chytrids are well placed to help us understand the evolutionary divergence of animals and yeast.

We also work with these species because of their impacts on human health and ecology; Naegleria gruberi is a model system for the 95% fatal brain-eating amoeba Naegleria fowleri, and we are studying cytoskeletal systems that are important for infection. We also study the frog-killing chytrid fungus that has decimated global amphibian populations. We are one of very few labs studying the basic cell and developmental biology of this organism that has had huge ecological impacts around the world.

Have you worked in other model systems before, and how does your current system compare to previous systems?

I have worked with Arabidopsis and various kinds of tissue culture cells (HL60s, fibroblasts, and Drosophila S2 cells). Although those systems had many tools and huge research communities, the cell biology of Naegleria and chytrids is so compelling that it more than makes up for it! Also, we do not have to worry about being scooped, which allows us to relax and enjoy doing science in an open and noncompetitive way.

What are the best and most challenging parts of using your model?

The best part of working with these species is how much cool biology we get to discover! Any time we put these cells on a microscope, there is a good chance we will see something that no one has seen before. It’s intoxicating and has led to a number of cool discoveries.

The most challenging part of working with our systems is the lack of existing tools. I often get asked “Why don’t you just use CRISPR?” Of course, we would love to do that! But first we need to develop methods to reliably introduce DNA, identify functional promoters, and test selectable markers, and so on. This means that we spend a lot of time adapting techniques and developing positive controls. We get really good at troubleshooting, which is awesome training for any scientific career path!

In your own words, can you describe the importance of using uncommon / non-model organisms in research?

There are so many important biological phenomena that are absent or very different in the small handful of well-established “model systems”. If we don’t work on other species, we will remain blind to this important biology.