Extreme Habitats: Microbial Life in Old Faithful Geyser
Pittsburgh, Pa., USA: An eruption of Old Faithful Geyser in Yellowstone
National Park is a sight to behold. Indeed, millions of tourists flock to
the park each year to see it. Hot water and steam are ejected in the air to
a height of 100–180 feet approximately every 90 minutes. Many adjectives
come to mind to describe it: powerful, mesmerizing, unique, otherworldly . .
. homey? Not so much. Yet new research by Lisa M. Keller, published on
earlier this year and to be presented on Sunday at the Geological Society of
America’s GSA Connects 2023 meeting, shows that for some microbial life
forms, Old Faithful Geyser is exactly that: home.
Meet Thermocrinis ruber and Thermus aquaticus. Thermocrinis ruber is the
most abundant bacterium residing in Old Faithful, making up over 60% of the
microbial population. As a chemoautotroph, it makes its own energy, not only
for its own sustenance, but also to the benefit of the rest of the microbial
community. But how? Old Faithful is a dark, hot place, which makes
photosynthesis impossible. Instead, Thermocrinis ruber takes CO2 outgassing
from the geyser and turns it into carbon forms that are potentially
cross-feeding heterotrophs in the community, such as Thermus aquaticus.
Both bacteria are extremophiles—life forms that thrive where most would not
survive. Whatever the challenging environmental factor, there are microbes
adapted to overcome it. Hypersaline pools? Check. Lack of oxygen? You bet.
Scorching hot water? Not a problem.
Geysers present a unique challenge: they are extremely dynamic environments.
As if being thrown hundreds of feet in the air every 90 minutes isn’t
disruptive enough, the microbes are subject to fluctuating steam and water
temperatures that constantly change throughout the eruption cycle.
In every challenge there is an opportunity, and Old Faithful’s thermal
excursions and eruptions are no exception. More strains of Thermocrinis are
found in Old Faithful than in any other non-geysing hot spring in
Yellowstone. “We think that the highly dynamic geyser environment creates
many different ecological niches that Thermocrinis can occupy, causing
increased sub-species level diversity,” says Keller. These findings show not
only that Old Faithful Geyser is habitable, but also that its dynamic
environment promotes genomic diversity.
In order to prevent any possible sample contamination, Keller collected
geysed water as it was falling from the eruption in weighted sterile bins.
Ten minutes after the end of the eruption she would walk out to the cone
with a National Park Service escort and retrieve the precious samples.
Additionally, she sampled a pool fed exclusively through Old Faithful’s
Once back in the laboratory, Keller incubated the samples at different
temperatures representative of geyser and pool conditions. The objective?
Monitor the microbial activity to verify that the sampled bacteria would
really be active at those extreme temperatures. And active they were, to
Keller’s delight. “They immediately showed signs of activity, suggesting
there is active microbial life in Old Faithful waters!” says Keller.
Beyond Earth, geysers are of extreme interest to the planetary community, as
active geyser eruptions have been observed on the moons Enceladus and
Europa. “Everybody gets excited about sampling Enceladus plumes,” says
Keller, “but prior to this work we didn’t even have terrestrial geysers
microbial samples. I thought, let’s take a step back and figure it out on
our own planet first.” Sampling planetary geysers may still be a long way
off, as the current methodology requires filtering liters and liters of
water—something that would certainly be challenging away from Earth—but now
that we know for sure that terrestrial geysers can host life, the race to
find it on planetary geysers is on too.
An Active Microbiome in Old Faithful Geyser
Author: Lisa M. Keller, Montana State University, firstname.lastname@example.org
17: T140. Hydrothermal Systems and Their Geologic Records
Sunday, 15 October 2023, 8:05–8:25 a.m.
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