In the steaming pools of California’s Lassen Volcanic National Park, life has found a way to thrive where most cells would begin to fall apart.
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cells → steam → way
Hidden in geothermal waters, a newly identified amoeba is pushing the known limits of how much heat complex life can tolerate, challenging long-held assumptions about the survival of cells with intricate internal structures, states an online report by
NASA.
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report → hide → NASA
The organism, named Incendiamoeba cascadensis and informally known as the fire amoeba, can reproduce at temperatures reaching 145°F (63°C), states the NASA website.
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website → name → F
It remains active at 147°F (64°C), moving through the scorching water in search of food.
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It → remain → food
Researchers also found that it can recover after being exposed to 158°F (70°C) for five minutes.
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it → find → minutes
The findings, published in Cell, establish a new upper temperature record for known eukaryotes.
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findings → publish → eukaryotes
According to NASA, the discovery is particularly striking because I. cascadensis is a eukaryote, a group whose cells are far more structurally complex than those of bacteria and archaea.
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cells → accord → bacteria
Eukaryotic cells contain a nucleus that protects genetic material along with membrane-bound structures such as mitochondria and the endoplasmic reticulum.
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that → contain → mitochondria
Those internal components perform essential jobs but can also create vulnerabilities under extreme conditions, the report adds.
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report → perform → conditions
Heat can cause proteins to lose their proper structure, damage DNA and destabilize cell membranes.
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proteins → cause → membranes
Researchers had previously suggested that the membranes surrounding eukaryotic organelles could not remain stable above about 144°F (62°C).
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membranes → suggest → °
As per the report, before its discovery, the upper temperature limit for eukaryotic life was about 140°F (60°C), based on a handful of heat-tolerant fungi and red algae.
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limit → base → fungi
The new organism demonstrates that at least one type of complex cell can function at significantly higher temperatures.
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type → demonstrate → temperatures
Built for a hostile environment
To understand how the amoeba manages such intense heat, the research team sequenced its genome and examined which genes became more active at different temperatures.
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genes → build → temperatures
The results revealed several potential survival strategies.
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results → reveal → strategies
Some genes help protect and stabilize DNA, while others are involved in sensing changes in the surrounding environment.
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others → help → environment
At elevated temperatures, genes associated with maintaining the correct folding of proteins became more active.
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genes → elevate → proteins
The researchers also identified proteins with unusually high positive surface charges.
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researchers → identify → charges
Similar characteristics have been observed in proteins produced by heat-loving bacteria and archaea, suggesting that some of the molecular strategies used to withstand extreme heat may cross the boundaries between very different branches of life.
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some → observe → life
The amoeba stops reproducing once temperatures rise above 145°F, but it can continue moving at slightly higher temperatures.
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it → stop → temperatures
Its ability to recover after a brief exposure to 158°F adds another layer to its unusual heat tolerance.
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ability → recover → tolerance
What makes an extremophile?
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What → make → extremophile
As per NASA, organisms capable of thriving under environmental conditions that would be lethal to most life are known as extremophiles.
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that → thrive → extremophiles
Those adapted specifically to extreme heat are called thermophiles.
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Those → adapt → heat
For an organism to qualify as a true heat-loving thermophile, it must be able to carry out essential activities such as growing, feeding, moving and reproducing above 113°F (45°C).
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it → qualify → F
Much of what scientists know about life in extreme heat comes from bacteria and archaea.
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scientists → know → bacteria
Their comparatively simple cellular organization is thought to make them better suited to environments where heat, acidity, radiation or other stresses can damage delicate cellular machinery.
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heat → think → machinery
Eukaryotes were considered more vulnerable because their cells contain numerous membrane-bound components.
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cells → consider → components
The fire amoeba suggests that this complexity does not necessarily impose such a strict temperature ceiling.
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complexity → suggest → ceiling
Clues for the search beyond Earth
The discovery also has implications far beyond Lassen Volcanic National Park.
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discovery → have → Park
Astrobiologists study extremophiles to understand the physical and chemical boundaries within which life can survive.
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life → study → which
Those limits can help scientists determine which environments on other worlds might potentially support life.
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environments → help → life
The researchers found another intriguing clue while comparing the amoeba’s genetic information with environmental DNA collected from geothermal sites around the world.
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researchers → find → world
Related sequences appeared in samples from places including New Zealand and Yellowstone National Park.
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sequences → appear → Zealand
That raises the possibility that I. cascadensis is not an isolated oddity.
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cascadensis → raise → possibility
Similar heat-tolerant amoebas could be living in geothermal environments elsewhere, waiting to be identified.
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amoebas → live → environments
The Aporia
