Earth’s Toughest Extremophiles: Extreme-Loving Organisms

Extremophiles: extreme survivors

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Most living things have very specific requirements when it comes to their environment. Take humans, for example; we need oxygen, water, nourishment, and many other things. If we were put into an extreme environment of high heat or pressure, for example, we simply wouldn’t survive. But where those environments may be incompatible with human life, there are some organisms that thrive here; they’re known as extremophiles.

What is an Extremophile?

What is an extremophile?

In the simplest terms, an extremophile is an organism that is able to thrive in hostile conditions where other lifeforms would never survive.

This can include environments with extreme temperatures, high levels of acid or alkalis, and even environments with incredibly high pressure, among others. When we look at the extremophiles found on earth, we can see that they live in the deep sea vents, frozen polar regions, hot springs, in underground rocks, and many other extreme environments.

But how do they survive in such demanding conditions? It all comes down to the unique adaptations of these organisms which occur at both cellular and molecular levels. This includes the presence of protective proteins and lipids as well as special enzymes such as the thermozymes of thermophiles.

While we may think that some environments simply aren’t habitable, extremophiles challenge our understanding of this. But what’s really interesting is that, since these organisms can thrive in such challenging conditions, it makes you question whether the extreme environments on other planets could, in fact, harbor life.

As a result of this, these organisms have become essential to scientific research, particularly in the areas of astrobiology. On top of this, their ability to live in such extreme situations has led to some interesting medical and biotechnological research. Even more interesting is that some microorganisms found in volcanoes are being used to look at how we can tackle climate change thanks to their ability to cycle gasses like methane. Off the back of this research, scientists are also able to develop potential new biofuels.

Beyond this, certain extremophiles are being used in medical research. One of the most well-known applications is the use of a particular enzyme that’s able to clone genes in both humans and animals. There’s also the potential for these extremophiles to be used in anti-cancer drugs, for creating lactose-free milk, and for the treatment of fungal infections.

Types of Extremophiles

Depending on where you look, there may be a number of different types of extremophiles. Some thrive in extreme temperatures, while others can withstand acidic environments that would make most creatures meet their demise.

Thermophiles (Heat-Loving Extremophiles)

Thermophiles (heat-loving extremophiles)

A thermophile is a type of extremophile that lives in extremely hot environments. In many cases, the temperatures here can exceed 122°F (50°C), but at the far end of the scale, may be as hot as 252°F (122°C)! In the case of most living things, this extreme heat would break down cells, proteins, and DNA and essentially cook the organism to death. But thermophiles are resistant to heat thanks to lipids within their cells that don’t become unstable when exposed to high temperatures. Moreover, their very DNA is able to repair itself in the event of heat damage.

These organisms are typically found in environments such as volcanoes, hot springs, and hydrothermal vents at the bottom of the ocean. Here, they’re not only exposed to high temperatures but also extreme pressure.

As well as the aforementioned adaptations, thermophiles are also able to ensure proper protein folding thanks to their specialized proteins that work differently in high temperatures. Additionally, these organisms produce enzymes that continue to function even when exposed to high heat and, as a result of this, scientists are able to look at ways in which this heat stability could be used in industry.

Halophiles (Salt-Loving Extremophiles)

Halophiles (salt-loving extremophiles)

Found in high-saline environments such as salt flats, salt pans, brine pools, and bodies of water like the Dead Sea, halophiles thrive in these salty conditions. In most cases, this level of salinity would not be compatible with life as the salt throws the osmotic balance of the cells out of whack. Essentially, the cells would lose too much water because of the presence of salt, thus killing the organism.

However, halophiles are specially adapted to these conditions and are able to regulate the water content of their cells despite the presence of salt. Within their cells, there are compounds called compatible solutes and these balance out the effects of the salinity in the environment.

But what’s even more interesting is that these organisms have the ability to produce enzymes that could be used in biotechnology owing to their ability to function when exposed to high-saline conditions. Humans are looking at how halophiles may be used in cosmetics as well as for food preservation. You’ve probably already eaten food preserved this way; soy sauce and herring in brine are two prime examples.

There are several different types of halophiles, including various bacteria and algae, which proves just how much diversity there is within these seemingly lifeless saline environments. In fact, they not only make up the biodiversity but even shape the landscape. Have you ever noticed the colored formations on salt flats? These are called microbial mats and are the result of halophiles. Our world would look very different without them. Not only this, but they’re important nutrient cyclers that impact the very dynamics of their ecosystems.

And it’s not just our world that halophiles may be shaping. Because of their resistance to salt, scientists use them to study the potential for life on other planets. Here on earth, they’re useful when researching and understanding salt tolerance, which can then be applied to things like crop rearing.

Psychrophiles (Cold-Loving Extremophiles)

Psychrophiles (cold-loving extremophiles)

We’ve explored heat-loving extremophiles, but on the other end of the scale are psychrophiles that thrive in freezing conditions. For you or I (and many other organisms) low temperatures slow down metabolism and interfere with cellular structures. But these extremophiles are perfectly adapted to live in the cold conditions of the polar regions, deep sea trenches, and among the glaciers.

They are primarily able to do this thanks to organic proteins that act as a natural antifreeze, protecting their DNA and preventing ice crystals from forming. Moreover, the enzymes produced by psychrophiles are much more easily able to function and become more flexible even when temperatures hit freezing.

But what’s really fascinating is that these extremophiles may even be able to help with climate change. They’re able to perform carbon cycling even at extremely low temperatures. On top of this, psychrophiles are important nutrient cyclers in the glaciers.

Thanks to their unique abilities, scientists are using psychrophiles to look at habitats in icy environments which may exist outside of our planet. Additionally, there is scope for them to be used to our benefit within medicine as well as in the food industry. For example, many psychrophiles are known to spoil food because of their ability to grow in freezing temperatures, but by researching and understanding this process, we can learn from it.

Alkaliphiles (Alkaline-Loving Extremophiles)

Alkaliphiles (Alkaline-loving extremophiles)

Where alkaline levels are high, most organisms would struggle with the extreme pH level which would interrupt the very biochemical processes that keep us alive. But there are some organisms, known as alkaliphiles that can be found in alkaline lakes, soda lakes, and other high pH environments, where they thrive. Some examples include the Octopus Spring in Yellowstone National Park and the Mono Lake at the Eastern Sierra in California.

In order to do this, these alkaliphiles are able to regulate their own pH despite high external alkaline levels. Moreover, their enzymes are not affected by the conditions and continue to function normally. The great thing about this is that scientists can use these enzymes in products like detergent as well as for waste treatment.

So adapted to life in extreme conditions are they that alkaliphiles require pH levels of at least 9.0 in order to thrive. Their specialized cell membranes are developed to continue functioning in these conditions. In other cases, these organisms have the ability to make their environment more acidic.

In any case, they’re pretty amazing and allow us to study things like habitability on other planets as well as biodiversity. Within their environments, alkaliphiles are known for their contribution to mineral precipitation, meaning they shape the very geochemistry of where they live.

Acidophiles (Acidic-Loving Extremophiles)

Acidophiles (acidic-loving extremophiles)

Where alkaliphiles love a high pH environment, acidophiles are found in geothermal acid springs, areas where mine waste reacts with water, and in volcanoes where the pH can be as low as 2.0. However, these organisms can be found in environments with a pH up to 5.0.

In any case, it’s pretty incredible that they can survive, and even thrive here since most organisms’ cells would not be able to cope with the high acid levels. But acidophiles have a natural ability to regulate their internal pH by pumping protons out of the space between their cells. What’s more, while acid may corrode most things, the cell membranes of acidophiles are perfectly adapted to resist this.

As with all extremophiles, the enzymes of acidophiles are specially adapted to function at extremely low pH levels. Humans have studied this ability and realized how these enzymes can be used in biotechnology. For example, the manufacture of biofuels.

Moreover, acidophiles have a unique ability to break down various compounds and elements, including some metals. To this end, we are able to use them to break down pollutants within a low pH environment.

Even in their natural habitats, acidophiles play a crucial role as they’re responsible for nutrient cycling which affect the geochemistry of their environment. There are many different types of acidophiles, including archaea and bacteria which allow us to study the potential for life in hostile environments we previously believed to be uninhabitable.

Barophiles (Pressure-Loving Extremophiles)

Barophiles (pressure-loving extremophiles)
Rogers AD, Tyler PA, Connelly DP, Copley JT, James R, et al. / Wikimedia Commons / CC BY 2.5

In the depths of the ocean, pressure is so high that most organisms’ cells would collapse. But that isn’t the case when it comes to barophiles, which are extremophiles that can withstand high pressure thanks to several adaptations.

Sometimes called piezophiles, these organisms put up with pressure that’s thousands of times higher than what we experience here on the surface. They’re able to do this thanks to a unique cell structure and membrane that doesn’t succumb to high pressure and instead, remains stable. There are special lipids in their cells that balance the extreme eternal pressure with the internal pressure.

Moreover, their enzymes are perfectly adapted to these conditions and even allow us to study their uses. In fact, scientists have already put them to use in things like bioremediation and food processing.

Often found in deep sea thermal vents and trenches, barophiles give us the opportunity to study how life can thrive in such intense conditions. They’re part of a complex community of microbial life in the ocean’s depths and play an important role in ecosystem dynamics and biogeochemical cycling.

Examples of Extremophiles

It’s plain to see that there are extremophiles all around the world that defy the very nature of life as we know it. Let’s take a closer look at some examples and how they survive.

Thermus aquaticus

Thermus aquaticus is a type of thermophile that is found in extremely hot environments such as thermal springs.
Food Research and Development Centre (Agriculture and Agri-Food Canada) / Wikimedia Commons / Public Domain

Thermus aquaticus is a type of thermophile that is found in extremely hot environments such as thermal springs. These organisms, which are a type of bacteria, are able to withstand and even thrive in temperatures as high as 176°F (80°C).

These bacteria take proteins from their environment and use them to support the cell membrane. Moreover, Thermus aquaticus possesses enzymes that make it tolerant to high temperatures. One of the most fascinating is Taq polymerase which has been a vital component in medical and forensic research owing to its use in polymerase chain reaction techniques that can be used to replicate DNA segments. But their uses don’t end there; the enzymes of these bacteria have also been used in pharmaceuticals and for the production of biofuels.

Looking at the genome of Thermus aquaticus, we can see how this species, and others like it, have various molecular adaptations that ensure their survival in their extreme habitats.

Pyrolobus fumarii

Pyrolobus fumarii can be found in the hydrothermal vents of the deep ocean, where temperatures can reach as high as 235ºF.
Mark Amend – NOAA Photo Library / Wikimedia Commons / Public Domain

Another interesting thermophile is Pyrolobus fumarii which can be found in the hydrothermal vents of the deep ocean, where temperatures can reach as high as 235°F (113°C). Yet, these amazing organisms continue to thrive.

Pyrolobus fumarii is a hyperthermophile, meaning it can cope with even higher temperatures, and this is partially because of its ability to produce its own energy using a process known as chemoautotrophy, which produces energy through the oxidation of sulfur. Moreover, these organisms produce enzymes that remain stable when exposed to high heat, which is essential to biotechnological research.

Not only can these extremophiles cope with high temperatures, but they’re also able to withstand the extremely high pressure of the deep sea as well as the high mineral content of their environments.

Dunaliella salina

Found in salt flats, salt lakes, and other high-saline environments, Dunaliella salina is a type of halophile that can survive in salinity levels over 30%.

Found in salt flats, salt lakes, and other high-saline environments, Dunaliella salina is a type of halophile that can survive in salinity levels over 30%. Consider that the ocean is only around 3.5% salt, and it’s easy to see why most other life would fail to survive in such extreme conditions.

Living in these conditions means that Dunaliella salina needs a way to produce energy and, being a type of algae, it does through the process of photosynthesis. Moreover, the organism has adapted to survive in high saline environments through the ability to prevent cell dehydration.

But perhaps one of the most interesting things about Dunaliella salina is how it can be used by humans. In its natural environment, Dunaliella salina produces pigments that protect it from UV radiation as well as beta-carotene which has antioxidant properties. Because of this, Dunaliella salina is often used in the production of dietary supplements and cosmetics.

Halobacterium salinarum

Halobacterium salinarum is a type of halophile known for its ability to thrive in high salinity environments such as salt pans and salt lakes.
Helga Stan-Lotter & Sergiu Fendrihan / Wikimedia Commons / CC BY-SA 4.0

Halobacterium salinarum is a type of halophile known for its ability to thrive in high salinity environments such as salt pans and salt lakes. The conditions here are intense and often have ten times the salinity levels of the ocean, making it impossible for most life to survive. Normally, this type of archaea thrives best where salinity levels are 20% or more.

Most people associate photosynthesis with plants, but these microscopic organisms, similar to bacteria are also able to complete this process to gain energy. They use a version of this called retinal-based phototrophy, which is not the same process used by plants. Additionally, Halobacterium salinarum is equipped with special pigments that are adapted to capture light. 

Within the cells of Halobacterium salinarum there are many potassium ions which allow for perfect osmotic balance, meaning the organism can survive in high saline conditions.

Scientists are not only studying how Halobacterium salinarum can be used in biotechnology but also how there could be potential for similar lifeforms to thrive on other celestial bodies besides earth.

Natronomonas pharaonis

Another organism that’s raised the question of whether life could thrive on other planets because of its ability to survive in extreme conditions is Natronomonas pharaonis. This is a type of alkaliphile typically found in salt lakes and flats where the pH level is extremely high. In a lot of cases, it may exceed 10.5, but this is vital to the growth of the organism.

Where Natronomonas pharaonis grows, you may notice pink or red colors forming in the environment. This is thanks to bacterioruberin (a special type of pigment) that the Natronomonas pharaonis uses to protect itself from the UV radiation of the sun.

And where the sun is concerned, it also comes in handy for photosynthesis as Natronomonas pharaonis also uses a retinal-based process in order to make its own energy.

But this isn’t the only way that it survives in high pH conditions. Natronomonas pharaonis is also able to produce potassium ions within its cells which ensure stable osmotic balance. So successful is it at surviving that Natronomonas pharaonis is one of the main extremophiles used in research to study extremophilic life. Not only this, but owing to its antioxidant properties, it’s also been studied for use in biotechnology.

Alkalihalobacillus alcalophilus

Found in alkaline soils, soda lakes and other environments with a high pH, Alkalihalobacillus alcalophilus is a type of alkaliphile that can thrive where the pH is as high as 11.0! In fact, most examples of Alkalihalobacillus alcalophilus require a pH of at least 9.0 in order to grow.

But how does it survive in such extreme conditions? It all comes down to the Alkalihalobacillus alcalophilus’ ability to produce enzymes that remain stable even when exposed to high levels of alkaline. This is not only useful in nature but also for humans who can use these enzymes where stability is required in high pH conditions. Food processing and the production of detergents are just some examples of this.

Owing to their ability to survive in high pH conditions and because they have been found in wastewater, scientists are also looking at how Alkalihalobacillus alcalophilus can be used to remedy contaminated soils and remediate wastewater.

Psychrobacter spp.

A psychrophile, Psychrobacter spp is often found in the earth’s polar regions as well as in the deep ocean and in alpine environments. They’re adapted to tolerate extremely cold temperatures as low as -4°F (-20°C).

They manage to thrive in these conditions thanks to a special enzyme that they produce, designed to continue functioning even at extremely low temperatures. What’s more, their cell membranes have far more fatty acids which makes them more fluid.

Where most other organisms would never survive in such cold conditions, Psychrobacter spp is able to continue producing energy to thrive. So effective are its natural processes that scientists use the enzymes it produces in biotechnological research.

Chlamydomonas nivalis

Chlamydomonas nivalis is a psychrophile which is often found in icy or snowy environments where temperatures can reach as low as freezing.

Chlamydomonas nivalis is a psychrophile which is often found in icy or snowy environments where temperatures can reach as low as freezing. It’s reported, however, that growth is fastest when the temperature is over 41°F (5°C).

In the alpine and polar regions that Chlamydomonas nivalis is found, most other life would never survive. However, owing to its ability to photosynthesize in low temperatures, this algae thrives where others can’t.

But these habitats are also exposed to high levels of sunlight and thankfully, Chlamydomonas nivalis has a way of coping with this. It produces a red pigment that protects it from UV radiation, and this is often seen in the form of watermelon snow.

Chlamydomonas nivalis is a vital member of its environment, performing nutrient cycling and thus creating food sources for others within the ecosystem.

Snottite spp.

The name Snottite spp might be pretty gross, but these acidophiles are anything but; in fact, they’re super fascinating single-celled bacteria that can survive in the most extreme acidic environments with a pH below 1.0! In fact, they even need these conditions to grow!

Snottites are typically found in mine drainage systems and caves where the pH is super low. Here, they make biofilm structures that look like stalactites which create an optimal environment for cells to exchange genetic material. These structures are also said to look like mucus strings; no prizes for guessing where the snottite gets its name!

Most other organisms wouldn’t survive in these conditions but Snottite spp not only tolerates low pH but is also specially adapted to live among toxic metal ions. They’re even known to cycle metals which ensures a healthy acidic environment which is further maintained owing the the snottites’ ability to produce sulfuric acid.

Acidithiobacillus spp.

Acidithiobacillus spp is an acidophile that thrives in areas of low pH, such as mine drainage and acidic soils.
Manfred Rohde, Helmholtz Centre for Infection Research, Braunschweig / Wikimedia Commons / CC BY 3.0

Acidithiobacillus spp is an acidophile that thrives in areas of low pH, such as mine drainage and acidic soils. These bacteria can oxidize sulfur and iron in their environments which not only contributes to their survival but also ensures biogeochemical cycling within their habitats. 

Generally found in areas where the pH is below 3.0, Acidithiobacillus spp is of particular interest to scientists because of its metal cycling abilities that make it useful in bioleaching processes.

Acidithiobacillus spp is usually a single-celled organism that requires these low pH levels to grow. Within their environments, they’ll even form biofilm structures that help them to survive.

Colwellia spp.

A type of barophile, Colwellia spp lives in areas where pressure is incredibly high. Most often, this is at the bottom of the ocean. In these conditions, most other life would fail to survive, but Colwellia spp has special enzymes that don’t collapse under high pressure. 

Not only are these anaerobic bacteria able to withstand high pressure, but they’re also adapted to deal with the often close to freezing temperatures at the bottom of the ocean, thousands of meters below sea level. In fact, in order to grow, Colwellia spp needs temperatures as low as -4°F (-20°C)!

Methanocaldococcus jannaschii

Methanocaldococcus jannaschii is typically found in the depths of the ocean in hydrothermal vents where it can withstand temperatures of up to 194°F (90°C), making it a hyperthermophile. What’s interesting is that it doesn’t just survive here, it actually needs these high temperatures to grow.

Down in the ocean’s depths, Methanocaldococcus jannaschii plays an important role in cycling biogeochemicals as well as producing methane.

Like many other thermophiles, Methanocaldococcus jannaschii produces the enzyme Taq polymerase, which has been invaluable in DNA research. These enzymes, along with others, remain stable under exposure to high heat, allowing this archaea to survive. Not only this, but Methanocaldococcus jannaschii is also adapted to high pressure and specimens have been found up to 8,530 feet (2,600 meters) under the surface.

Tardigrades (Water Bears)

Tardigrades, more commonly known as water bears, are special because of their ability to withstand various environmental factors.

Tardigrades, more commonly known as water bears, are special because of their ability to withstand various environmental factors. So adaptable are they that they’re found in many habitats like soil, water, moss, and polar regions. They’ll withstand extreme dryness, freezing temperatures and even the vacuum of space which has led scientists to question the possibility of life outside of our planet.

One of the reasons that they’re able to do this is because of their ability to enter a dormant state known as cryptobiosis. During this state, metabolism slows down so much that it almost stops, allowing them to survive where all other life would fail. In very dry conditions, this state also causes them to lose all of the moisture within their bodies.

Tardigrades (water bears)

And if you think that high pressure will stop them, then think again! Tardigrades can live at the bottom of the ocean just as easily as they can at the top of a mountain! Whether it’s hot or cold, these amazing organisms adapt to survive and can live in freezing temperatures as well as those up to 302°F (150°C).

They’re even resistant to radiation and have an ability to repair their DNA if it is damaged by extreme conditions.

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