Lifestyles of arbuscular mycorrhizal fungi



Examples of AM fungi hyphae (a, c) and
vesicles (b, d) in corn (a, b) and prairie roots (c, d).
Image from Bach et al. 2018, Ecology


By: Elizabeth Bach, Executive Director, Global Soil Biodiversity Initiative, School of Global Environmental Sustainability, Colorado State University

 

One of my first experiences with soil ecology was a summer Research Experience for Undergraduates, during which I got to spend a lot of time looking at arbuscular mycorrhizal fungi within roots. I had never really observed these microscopic relationships before, and seeing the ways the fungal bodies lived within the roots amazed me.  Hyphae extended out like fingers from the root, searching the soil for nutrients and water.  Vesicles appeared as small spheres, full of lipids that the fungus could consume for energy when the host plant quit delivering carbohydrates.

Fast-forward six years. I still loved working with soil microorganism and was a few years into a PhD program.  I had the opportunity to introduce this exciting microscopic world of mycorrhizal fungi to a couple of undergraduate assistants.  Over the course of several weeks of counting arbuscular mycorrhizal fungi on roots from corn (maize) and tallgrass prairie plants, these students, Giselle and Kira, noticed that the corn roots had more hyphae than the prairie roots and the prairie roots had more vesicles.  They asked why, and I didn’t know the answer, so we went looking in the scientific literature. Interestingly, we didn’t find many previous studies that could explain the pattern.

Giselle and Kira went back and specifically counted the rate of hyphae and vesicle presence on the roots, and it turned out corn roots had 6 times greater hyphal presence rate and prairie roots had 3 times greater rate of vesicle presence!  It also turned out that the rate of presence of these structures varied across the growing season, with hyphae colonization peaking in August for all roots, and vesicle presence peaking in July, for the prairie roots, and September, for corn roots.  Giselle and Kira shared their findings with poster presentations at our university (Iowa State University) and at national scientific meetings (American Geophysical Union and Ecological Society of America).

This data story remained interesting, but didn’t seem like enough to pursue a classic scientific publication. In 2017, the journal Ecology rolled out a new article type: The Scientific Naturalist.  The section is dedicated to short essays, sharing an observation of the natural world that captured the wonder of ecological discovery and could lead to new hypotheses and deeper research.  Immediately, Giselle and Kira’s work came to mind and I reached out to them to ask if they might be interested in working with me to write up their observations.  Over the next few months we, along with our lab group’s PI Kirsten Hofmockel and fellow AM fungi researcher Jonathan Bauer, worked to write-up our story to share.  The dynamic life of arbuscular mycorrhizal fungal symbionts was published January 24, 2018. It has been a delight to work with and learn from scientists from across the spectrum of experience on this project, and we are excited to see what future work may grow from this work!

 

Elizabeth Bach is Executive Director of the Global Soil Biodiversity Initiative housed in the School of Global Environmental Sustainability at Colorado State University.

Giselle Narvaze-Rivera is a Master’s of Science student in Physical and Biological Anthropology at Iowa State University.

Kira Murray is a consulting geologist at Freestone Environmental, Richland, WA.

Jonathan Bauer is a postdoctoral researcher at Michigan State University

Kirsten Hofmockel is Lead Scientist for Integrative Research at the Environmental Molecular Science Laboratory at Pacific Northwest National Laboratory.

 

Original Article:

Bach, E.M.; Narvaez-Rivera, G.; Murray, K.; Bauer, J.T.; Hofmockel, K.S. 2018. The dynamic life of arbuscular mycorrhizal fungal symbionts. Ecology doi:10.1002/ecy.2096

Tags: