Heterotrophic Protists as Useful Models for Studying Microbial Food Webs in a Model Soil Ecosystem and the Universality of Complex Unicellular Life

• Main Author: Thompson, Andrew Robert
• Format: Text
• Language: unknown
• Published: BYU ScholarsArchive 2019
• Subjects: heterotrophic soil protists; McMurdo Dry Valleys; shotgun metagenomics; network analysis; life on Mars; key evolutionary innovations; universal complex unicellular life; Life Sciences; Microbiology; Antarctic; The Antarctic; Antarc*; Antarctica
• Online Access: https://scholarsarchive.byu.edu/etd/8575; https://scholarsarchive.byu.edu/context/etd/article/9575/viewcontent/etd10945.pdf

Heterotrophic protists, consisting largely of the Cercozoa, Amoebozoa, Ciliophora, Discoba and some Stramenopiles, are a poorly characterized component of life on Earth. They play an important ecological role in soil communities and provide key insights into the nature of one of life’s most enigmatic evolutionary transitions: the development of the complex unicell. Soil ecosystems are crucial to the functioning of global biogeochemical cycles (e.g. carbon and nitrogen) but are at risk of drastic change from anthropogenic climate change. Heterotrophic protists are the primary regulators of bacterial diversity in soils and as such play integral roles in biogeochemical cycling, nutrient mobilization, and trophic cascades in food webs under stress. Understanding the nature of these changes requires examining the rates, diversity, and resiliency of interactions that occur between soil organisms. However, soils are the most taxonomically diverse ecosystems on Earth and disentangling the complexities of dynamic and varied biotic interactions in them requires a unique model system. The McMurdo Dry Valleys of Antarctica, one of the harshest terrestrial environments on Earth, serve as a model soil ecosystem owing to their highly reduced biological diversity. Exploring the functioning of heterotrophic protists in these valleys provides a way to test the applicability of this model system to other soil food webs. However, very little is known about their taxonomic diversity, which is a strong predictor of function. Therefore, I reviewed the Antarctic literature to compile a checklist of all known terrestrial heterotrophic protists in Antarctica. I found significant geographical, methodological, and taxonomic biases and outlined how to address these in future research programs. I also conducted a molecular survey of whole soil communities using 18 shotgun metagenomes representing major landscape features of the McMurdo Dry Valleys. The results revealed the dominance of Cercozoa and point to an Antarctic heterotrophic protist ...