Extremophiles: Earth Analogs for Alien Life

Venus has a thick, toxic atmosphere made mostly of carbon dioxide and sulfuric acid. Yet phosphine gas, a biomarker on Earth, has been detected in the atmosphere.

Astrobiologists have yet to find conclusive proof of life outside Earth, although tantalizing clues of the possibility of life do exist. Just this week, researchers announced the discovery of phosphine gas in the clouds of Venus. Phosphine is found in Earth’s atmosphere and is mostly of biogenic origin, created by certain anaerobic bacteria. The phosphine on Venus is of too high a concentration to be easily explained by non-biogenic sources such as lightning; life could be a possible explanation, but that life would have to survive in an extreme environment, since the clouds of Venus are 96% sulfuric acid.

To understand what such life might be like, we study organisms on Earth that can survive and even thrive in extreme conditions, including high acid environments. These extremophiles are an analog of what we could look for on Mars, under the ice of Enceladus or Europa, or in the clouds of Venus. By studying extremophiles, we train ourselves how to study life elsewhere.

The following short articles were researched and written by students at New Haven School in Spanish Fork, Utah as part of their astrobiology summer course. Because privacy concerns, I am only providing their initials.

The surface of Venus is hot enough to melt lead, has a pressure as great as 26 Earth atmospheres, and rains sulfuric acid. You would die horribly four different ways if you stepped foot outside without a spacesuit.

Acidophiles by V. N.

An acidophile is a bacteria / animal that can or must survive in a highly acidic area. An acidic environment is an area that has a pH level below 6. An organism is only considered an acidophile if it can thrive in an area with a pH below 2, areas such as that are considered highly acidic. Acidophiles are able to survive in highly acidic environments due to their membrane system which pumps out protons into the intercellular space; the result helps keep the cytoplasm at or around a neutral pH. Due to this process it is not necessary for intracellular proteins to develop acid stability.

Certain acidophiles such as Acetobacter aceti utilize an acidified cytoplasm, this forces out nearly all of the proteins in the genome to get to acid stability. The Acetobacter is a great way to understand how proteins can obtain acid stability. Many studies focused on acidophiles have shown a few mechanisms by which the acidophiles obtain a steady amount of acid inside them. In most stable acid proteins there tends to be too much acid residue which affects low pH stabilization created by a buildup of positive charges. Other ways acidophiles survive is by minimizing the solvent accessibility of acid residues, or by binding the metal cofactors.

Acidophiles are incredible at adapting to harsh environments. It is notable that acidophiles can survive in an impressive amount of harsh and unwelcoming environments that humans couldn’t imagine or physically stay alive in.

Alkaliphiles by K. T.

Did you know harsh environments can sustain living organisms? These organisms are known as extremophiles. The definition of an extremophile is “a microorganism, especially an Archaean, that lives in conditions of extreme temperature, acidity, alkalinity, or chemical concentration.” (Dictionary, Definition of Extremophiles, google.com). Within extremophiles are classes, such as alkaliphiles. These species are known to grow around a pH of 10. Certain microbes qualify as this specific class.

An alkali bee with nesting hole. These bees thrive in highly alkaline soils, with pH around 10.

Alkali bees are a suitable example for an animal that can survive a harsh environment. Alkali bees dig nests underground looking for salty soil, this is categorized as an haloalkaliphile. They create a strategic arrangement of tunnels to lay eggs in safety. Their lifestyle is isolated and not livable for other creatures, but they adapt to it quite easily, since it is in their nature to do so (Alkali Bees, fs.fed.us.com).

Other categories known are the obligate and facultative alkaliphiles. Obligates require a very high pH to survive, and facultative are able to survive in high pH climates, but also are adaptable to normal conditions (en.wikipedia.com, Alkaliphile). Alkaliphiles are still currently being discovered and not very much is known about them in this present day. Even though there is little information, the research continues to explore more about the adaptations and creatures surviving under these harsh, unlivable climates.

Clostridium by S. E.

Clostridium is an anaerobe, a type of extremophile which can survive without oxygen, metabolizing on their own without external energy (oxygen). They are also a genus of Gram-positive bacteria, which means they change into a certain color when exposed to a staining method introduced in 1884 by Hans Christian Gram. Clostridium is commonly known in the medical world because this specific type of anaerobe is known to cause and accelerate human pathogens by infecting the intestinal and digestion tracts by overproducing healthy fiber, overloading the dietary system; often appearing as Clostridium perfringens (food poisoning) or Clostridium tetani (tetanus) in the body, this genus can cause many infections which, like the latter condition of tetanus or lockjaw, can sometimes be fatal.

Clostridium frequently exists in airtight containers, as it is able to survive anaerobically, or without air, causing food poisoning to those who eat canned goods infected by this anaerobe. A prokaryote, or a bacterium lacking sophisticated internal systems, Clostridium is sometimes classified as a disease. As for anaerobes in general, other substances and energies than oxygen are used in metabolism and respiration, such as nitrates. They do best in regular body temperature environments, unlike other extremophiles which can survive in severe temperatures.

Clostridium, a type of anaerobic bacteria that can thrive without oxygen in airtight containers. If it gets into foods, it will produce toxic byproducts that cause food poisoning.

Clostridium strains cause disease and infection by secreting toxins in lysis, the organelle process in which the cell membrane is ruptured by viral infections. In closing, Clostridium is a bacterium, often rod shaped, and the cause of toxins that can be potentially fatal and are often very resilient due to their status as anaerobes.

Halophiles by N. D.

Halophiles are a type of extremophile that thrives in environments with high concentrations of salt. The name “halophile” comes from the Greek words “salt loving.” Halophiles mainly live in evaporation ponds or salt lakes. Some examples are The Great Salt Lake, Owens Lake, and the Dead Sea. Those bodies of water contain a salinity of 33.7%. That’s about 10 times saltier than any ordinary seawater. That amount of salt allows halophiles to thrive in their environment.

Halophiles are chemoheterotrophs, using light for energy and methane as a carbon source under aerobic or anaerobic conditions. Halophiles contain proline, amino acid derivatives, polyols, sugars, and methylated sulfur compounds. Halophiles are a very complicated and detailed organism that is difficult to study. Most halophilic and other salt eating animals use energy to remove salt from their cytoplasm. Normally, organisms living in salt would lose water and die because of osmosis—other than halophiles.

The Spiral Jetty in the north arm of the Great Salt Lake. The pink color of the water is caused by a halophilic bacteria that stains the water pink.

Halophiles are categorized by the levels of salt on which they grow best: slight halophiles, moderate halophiles, and extreme halophiles.

Hyper Piezophiles by L. M.

Hyper Piezophiles are organisms that survive and reproduce in high pressures in the depths of the ocean or deep underground, also known as the deep biosphere. In order for these organisms to live in these extreme environments they develop various mechanisms to prevent the effects of the elevated pressures they live through. They live more than 1000 m below sea level, which has a hydrostatic pressure greater than 10 MPa. In the deep biosphere there is lack of light and nutrients and very little organic materials.

When piezophiles are isolated they can be divided into thermopiezophiles and psychropiezophile. Pyroccus yayanosii strain CH1 is the only known thermopiezophile and is found in hydrothermal vents. Hydrothermal vents are splits in the ocean’s floor where water is geothermally heated up to 400°C and emitted and then results in eutrophic, microbial dense communities. Psychropiezophiles are found in the depths of the ocean also, but in areas that are not heated by geothermal energy that reaches about 2°C.

Osmophiles by B. H.

There are probably a lot more creatures living in your food than you think. Osmophilic organisms are adapted to live in areas with high sugar like jam or honey. The adaptations that osmophilic organisms have are they can make glycerol to balance their internal and external osmotic pressure. They can also shrink their membranes to keep the glycerol in their cells. Yeasts are common osmophilic organisms you might discover in foods containing high amounts of sugar. Some types of yeast, molds, and bacteria are osmophilic.

Osmophilic organisms are some of the only organisms that are adapted to live in high osmotic pressures. A lot of different foods have sugar in them because the sugar will suck up all the water around it, making it a great food preservative. I don’t know about you but I know that now I will look at food totally differently and will be more careful about what I eat. I don’t want to get sick or even risk getting sick. The bacteria that lives in your food can be either good or bad; be sure you are not eating a bunch of bad bacteria.

Too Hot to Handle: The Weird World of the Pompeii Worm

by J. W.

The Pompeii worm lives at hydrothermal vents in the deep ocean under high pressure, with extreme heat at its head and cold at its tail

Imagine living comfortably in 140-degree water. Seems impossible, right? Not for the Pompeii worm. Discovered by marine biologist Craig Cary and his colleagues in 1997, the Pompeii worm (scientific name Alvinella pompejana) is a species of deep-sea polychaete worm, or “Bristle Worm.” Pompeii worms can reach up to 13 centimeters in length. They have a feather-shaped head and tentacle-like gills, colored red by hemoglobin. Pompeii worms live in tubes near “black smokers” — hydrothermal vents on the Pacific seabed that emit a substance comparable to black smoke. These worms are extremophiles, organisms that can live comfortably under multiple extreme conditions. For the Pompeii worm, those conditions are extremely high pressure and temperatures.

In fact, the Pompeii worm is known as the most heat-tolerant animal on Earth. Alvinella pompejana can survive at sustained temperatures of 105 ° C (221 ° F) for short periods of time, but it is most comfortable in temperatures ranging from 40 to 60 ° C (113 to 140 ° F). Pompeii worms like to keep a cool head– while they rest their tails in water with temperatures as high as 80 °C (176 ° F), they rest their heads in cooler water, at temperatures around 22 ° C (72 ° F).

The Pompeii worm’s abilities to withstand the heat are linked to heat-stable ribosomal DNA and a symbiotic relationship with bacteria. The worms have hairy-looking backs; these “hairs” are actually colonies of bacteria, which feed off of mucus secreted from glands on the worm’s back. This layer of bacteria can be up to one centimeter thick! The bacteria are thought to provide insulation for the worm, thanks to eurythermal enzymes that protect the bacteria– and thus, the worm– from extreme temperatures. It’s clear– no one can take the heat like the Pompeii worm.

Extremophiles: Snottites by S. S.

Snotticles hanging from the ceiling of a cave in New Mexico. The mucus-like material is created by an extremophile that lives in the caves without light and is chemotrophic.

Extremophiles are organisms that live in extreme conditions. An example of an extremophiles is Picrophilus torridus, it is a thermoacidophile adapted in hot acidic conditions. It was found in soil near a hot spring in Hokkaido, Japan. Snottites or Snoticles are another extremophile that are found in caves hanging from the walls and ceilings. They have the consistency of nasal mucus and look like drips. Snottites got thier name by Jim Pisarowicz in 1986. They get their energy from chemosynthesis of volcanic sulfur compounds including H2S and warm water solution dripping down from above. Because of this their waste is highly acidic with similarities to battery acid. Diana Northup and Penny Boston brought attention to snottites while studying in a toxic sulfur cave called Cueva de Villa Luz in Tabasco, Mexico. Northup says that at certain times of the year the slime makes the walls look like they have been silvered, she says that “it’s just breathtakingly gorgeous.” Some cave systems Snottites are found in are the Frassasi caves in Italy, Grotta di Rio Garrago, and Cueva Luna Azufre.

Tardigrades by S. W.

Tardigrades are incredible and extremely resilient microscopic animals. Although they look soft and puffy, they are actually covered in a tough cuticle closely related to that of a grasshopper. First discovered in 1773 in Germany by J.A.E Goeze, these tiny extremophiles were named “Kleiner Wasserbär” or “little water bears” in English. In the grand scheme of time, Tardigrades were discovered a long time after the start of their existence. Scientists have traced them back to roughly 4 million years before the oldest of our found dinosaurs.

As of today, roughly 1,300 species of Tardigrade have been found and can be properly classified each of which share some similar features. All Tardigrades have four to six claws on each of their eight feet used to easily allow them to cling to plant matter. They all have a mouth-like structure known as a buccopharyngeal apparatus used to suck in nutrients from plants and other microorganisms.

A tardigrade, or little water bear. These microscopic creatures like wet, mossy environments but can survive extreme dryness lasting years by rolling into a ball which preserves moisture. They are protected from radiation by a layer of protein on their cuticles.

Tardigrades have been nicknamed “Moss Piglets” due to their preference to live in mossy areas with lots of fresh water moisture and their slight resemblance to tiny, grey pigs. Although they prefer wet areas, Tardigrades have been proven to thrive even in desert sand dunes because they keep an extremely thin yet useful layer of water around their bodies at all times. Because they keep themselves moisturized so well, Tardigrades can actively survive without food or water for up to thirty years.

Tardigrades have incredible resilience to many different substances. They have a unique protein in their bodies called a Damage Suppressor or “Dusp” in shortened terms. This amazing protein protects them against extreme radiation which can be present in soil, water and around plant life. These damage suppressing proteins also allow them to survive at a temperature of up to – 328 ° F (- 200 ° C) or beyond boiling, in pressures six times harsher than in the deepest of our ocean’s trenches and they can withstand the cold vacuum of outer space for an impressive amount of time. Although it may seem so, these tiny superbeings are not immune to everything. They are very sensitive to acidity. Even the lowest levels of acidity can kill them almost instantly.

Known also as “masters of cryobiosis,” Tardigrades can practically freeze themselves in time and wait for unsafe conditions to pass by. Cryobiosis is a state of complete inactivity triggered by a lack of moisture. Tardigrades can squeeze themselves into tight balls tucking down their heads for protection. This allows them to release moisture through their skin like a living microscopic sponge. When their surrounding conditions improve, Tardigrades can quickly consume moisture and revive themselves.

Thermophiles by C. L.

Alicyclobacillus acidocaldarius are a thermophile species. These creatures can inhabit an environment with a higher temperature than most species can survive in. The first species of alicyclobacillus were found in the geysers in Yellowstone National Park, and also found in fumarole soil, which is an opening near a volcano in which hot gasses come out. They can be found in Hawaii’s Volcano National Park. Scientists decided that it should be classified as Bacillus acidocaldarius in 1971, then later on figured out that studies showed it to be from a different and new species called Alicyclobacillus. They live in acidic and high temperatures. Thomas D. Brock was one of the first scientists to categorize this species. The temperature in which Alicyclobacillus can grow at is 60-65 ° C, and optimum pH it can grow at is 3.0-4.0, which is a significant amount of acid. Over time they have adapted to the high acidic levels of their environments.

Grand Prismatic Spring in Yellowstone National Park. The rainbow of colors is created by different species of thermophilic bacteria that can live in the varying temperatures and high acidity of the water.

Hyperthermophiles by R. R.

Hyperthermophiles were first discovered by Thomas D Brock in 1965, isolated from the hot springs in Yellowstone National Park. There are now 70 species of Hyperthermophiles. The most extreme living on the walls of deep sea hydrothermal vents, a place one would normally see as impossibly habitable. What gives hyperthermophiles this incredible ability to endure and even thrive at such high temperatures actually has something to do with their protein molecules and cell makeup. Their protein molecules, which show hyperthermostability, allow them to maintain structural stability and function at high temperatures. These evolved hyper thermostable proteins allow chemical reactions within the organism to proceed faster at higher temperatures. Hyperthermophiles also contain high levels of saturated fatty acids in their cell membranes which allow them to retain their shape at their preferred temperature.

Hyperthermophiles live in hydrothermal vents, which are created by volcanic activity and tectonic plate movement. It is a fissure on the seafloor from which geothermically heated water comes from that can reach temperatures above 700 °F in some cases. There are two types of hydrothermal vents, black smokers and white smokers. Black smokers emit particle laden fluid that are made up of fine-grained sulfide minerals formed when the hydrothermal fluids mix with the very cold sea water surrounding the vents. White smoker vents have lighter minerals emitted and lower temperatures than that of black smoker vents. The mineralized fluids from this type of vent are rich in calcium and sulfate-rich and form carbonate deposits. Any creature able to withstand and thrive in such an environment is astounding.

About davidvblack

I teach courses in multimedia, 3D animation, Earth science, physics, biology, 8th grade science, chemistry, astronomy, engineering design, STEAM, and computer science in Utah. I've won numerous awards as an educator and am a frequent presenter at state and national educator conferences. I am part of the Teachers for Global Classrooms program through the U.S. Department of State and traveled to Indonesia in the summer of 2017 as an education ambassador. I learned of the Indonesian education system and taught classes in astronomy and chemistry at a high school near Banjarmasin in southern Borneo. I am passionate about STEAM education (Science, Technology, Engineering, Arts, and Mathematics); science history; photography; graphic design; 3D animation; and video production. This Spaced-Out Classroom blog is for sharing lessons and activities my students have done in astronomy. The Elements Unearthed project (http://elementsunearthed.com) will combine my interests to document the discovery, history, sources, uses, mining, refining, and hazards of the chemical elements.
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