Syracuse University biologists are studying how microbial eukaryotes thrive in the harsh environment of geothermal lakes. It is estimated that there are approximately 8.7 million species of eukaryotes on Earth. Eukaryotes are characterized by a nucleus and other membrane-bound organelles within the cell. Although people often associate eukaryotes with animals and plants, these forms of eukaryotes actually make up only two of the six major categories of eukaryotes.
Oliverio and Rappaport spent the summer conducting field research in California's Lassen Volcanic National Park, which is home to many hydrothermal landforms. Source: Syracuse University
A large portion of eukaryotic diversity consists of single-celled microorganisms called protists. By studying these organisms, scientists can explore the evolutionary paths that account for the rich diversity and complexity of eukaryotes. Through these studies, we can learn about the development of animal life on Earth, such as the emergence of multicellularity.
As researchers work to better understand the mechanisms behind the evolution of Earth's species, questions remain about how microbial eukaryotes adapt to Earth's extreme environments. To delve further into this question, scientists in the College of Arts and Sciences (A&S) Biology Department are currently studying native organisms that inhabit some of the harshest environments on Earth: extremely hot and acidic geothermal lakes.
A&S biologists Angela Oliverio (left) and Hannah Rappaport at the largest geothermal lake in the United States at Lassen Volcanic National Park in California. Image source: Syracuse University
A team led by Assistant Professor of Biology Angela Oliverio recently returned from Lassen Volcanic National Park in California, home to the largest geothermal lake in the United States.
"The lake is an acid sulfate vapor heated geothermal feature, which means it is both quite hot (about 52°C/124°F) and acidic (about pH 2)," said Oliverio, who will begin working at Syracuse University in 2022. "This makes it a very unique environment to study multiextreme acidophiles, which are organisms that are adapted to two or more extreme conditions - in this case, high temperature and low pH."
So how did they know to search for microbial eukaryotic life in a thermal lake in California? Recently, Oliverio and Hannah Rappaport, a researcher in Oliverio's laboratory, jointly published a research paper in Nature Communications. In this paper, the research team established a database that includes previous research on the search for microbial eukaryotic life in extreme environments. Specifically, they analyzed which eukaryotic lineages were detected multiple times in different studies under similar environmental conditions.
Image of an amoeba (round gray blob in background) and red algae (four white ovals in foreground) taken by Hannah Rappaport using a light microscope. The samples were taken from a geothermal lake in Lassen Volcanic National Park. Image source: Syracuse University
"We found that there are several amoeba strains that tend to be found in extremely high-temperature environments," Oliverio said. "This suggests that studying these strains may have significant implications for how eukaryotic cells adapt to life in extremely high-temperature environments."
According to Oliverio, a special study conducted by the Gordon Wolfe Laboratory at California State University, Chico showed that a type of amoeba called thermomoebae is abundant in the geothermal lake in Lassen National Park. However, there are currently no genomic data for this organism. Determining how this creature adapted to such extreme environments could expand our understanding of what types of environments in the universe are suitable for life.
Last summer, Oliverio and Rappaport traveled to Lassen National Park to learn more about this special protist and to search for other new extremophilic eukaryotes. At the lake's edge, the team used a long painter's bamboo pole with a 1-liter bottle stuck on top to collect samples—no small feat considering that the lake water is well over 100 degrees Fahrenheit. The bottles were then shipped back to Oliverio's lab at Syracuse University, where the team is now isolating single cells for genome sequencing and observing the amoeba's characteristics under a microscope.
Syracuse University researcher Hannah Rappaport dipped bottles into the hot lake to collect samples. Because of the warm water temperatures and unstable ground, researchers must maintain a safe distance while collecting samples. Image source: Syracuse University
While much is still unknown about how eukaryotes adapt to extreme environments, Oliverio hopes this research will help fill some of the current gaps in knowledge.
Image of an amoeba (round gray blob in background) and red algae (four white ovals in foreground) taken by Hannah Rappaport using a light microscope. The samples were taken from a geothermal lake in Lassen Volcanic National Park.
"We suspect there is something special about this amoeba morphology that allows it to persist in these eukaryotic lineages, but the mechanism remains unknown," she said. "Based on our study, we hypothesize that horizontal gene transfer (the movement of genetic information between organisms) and genome pruning (when a genome deletes genes it does not need) from bacteria, as well as the expansion of particularly useful gene families, may be a few ways in which protists acquire a toolkit to survive in extreme environments."
The team's genome-scale discovery will provide important missing data for reconstruction of the tree of life. "This will further deepen our understanding of the distribution and evolution of life on Earth."