Assistant Professor of Biology Dr. Stephanie Carr

Hartwick’s Carr Helps Show How Unusual Microbes Hold Clues to Early Life

March 21, 2019

Hartwick College Assistant Professor of Biology Dr. Stephanie Carr ’06 recently helped complete a new study revealing how a group of deep-sea microbes provide clues to the evolution of life on Earth.

Carr was part of a research team from Bigelow Laboratory for Ocean Sciences in Maine − including the University of Hawaii, and the Department of Energy (DOE) Joint Genome Institute − that analyzed how microbes called Hydrothermarcheaota live and thrive in the hot, oxygen-free fluids that flow through Earth’s crust.

The results of the team’s research were published in The ISME Journal: Multidisciplinary Journal of Microbial Ecology last month.

“Studying these unique microbes can give us insights into both the history of Earth and the potential strategies of life on other planets,” said Carr, first author on the paper. “Their survival strategies make them incredibly versatile, and they play an important, overlooked role in the subsurface environments where they live.”

Carr and her fellow researchers used cutting-edge molecular methods to study these microbes, which live in such an extreme setting that they have never been cultivated in a laboratory for study.

The team bypassed that problem though genetic sequencing methods, including single cell genomics, a suite of novel techniques that detect and sequence individual cells. They found that Hydrothermarcheaota may obtain energy by processing carbon monoxide and sulfate, and using energy from this process to grow.

Analyzing Hydrothermarcheaota genomes also revealed that these microbes belong to the group of single-celled life known as archaea, and evolved early in the history of life on Earth – as did their unusual metabolic processes. These observations suggest that the subsurface ocean crust is an important habitat for understanding how life evolved on Earth, and potentially other planets.

The researchers also found genetic evidence that Hydrothermarcheaota have the ability to move on their own. Motility offers a valuable survival strategy for the extreme environment they call home, which has a limited supply of nutrients essential to life.

Hydrothermarcheaota were initially discovered in 2011, when a team of scientists sailed to the flank of the Juan de Fuca Ridge, a mid-ocean ridge off the coast of Washington State, where two ocean plates are separating and generating new oceanic crust. They used a deep-diving robot from Woods Hole Oceanographic Institution to travel 2.6 km to the seafloor and collect samples of the fluid that flows through the deep crust.

These fluid samples contained microbes that had never before been studied. Working in partnership with the Department of Energy’s Joint Genome Institute, the researchers sorted and analyzed the microbes in the Single Cell Genomics Center at Bigelow Laboratory in Los Angeles. These analyses yielded insights into the genetic blueprints of Hydrothermarcheaota, their relationship to other specific single-cell organisms, and the strategies they have evolved to survive in the subseafloor.

“The majority of life on Earth is microbial, and most microbes have never been cultivated,” said Beth Orcutt, a senior research scientist at Bigelow Laboratory and the study’s senior author. “These findings emphasize why single cell genomics are such important tools for discovering how a huge proportion of life functions.”

Carr and the researchers hope to build upon their discoveries when they return to the Juan de Fuca Ridge this May to continue investigating the extreme microbes thriving below the seafloor.

Also joining the team is Tylisha Gourdine ’20, who, along with Carr, will be responsible for measuring the gaseous geochemistry of the crustal fluids and attempt to culture new or unique organisms, such as those from the phylum Hydrothermarchaeota.

The project was supported by the National Science Foundation, the NASA Astrobiology Institute, the DOE Joint Genome Institute, and the Center for Dark Energy Biosphere Investigations (C-DEBI).