6.1 - Extremophiles

Question 1

What are extremophiles?

Answer 1

Extremophiles are organisms that are able to survive and thrive in extreme environments that are typically hostile to most other forms of life. These environments can include extreme temperatures (both hot and cold), high pressure, high salt concentrations, low pH, high radiation, and other extreme conditions.

Extremophiles are found in a wide range of habitats, including deep sea hydrothermal vents, hot springs, acid mine drainage, salt flats, and other extreme environments. They include both prokaryotic and eukaryotic organisms, such as bacteria, archaea, fungi, and algae.

The ability of extremophiles to survive in extreme environments is due to a range of adaptations, including specialized enzymes, membrane systems, and metabolic pathways that are able to function under extreme conditions. Studying extremophiles and their adaptations has provided valuable insights into the limits of life on Earth and the potential for life on other planets or moons with extreme environments.

Some examples of extremophiles include thermophiles, which are able to survive at high temperatures (typically above 45 °C), halophiles, which can survive in high-salt environments, and acidophiles, which can survive in extremely acidic environments. Other extremophiles include psychrophiles (cold-loving organisms), barophiles (pressure-loving organisms), and radioresistant organisms, which can survive high levels of ionizing radiation.

Question 2

What are most extremophiles?

Answer 2

Most (not all) extremophiles are single called archae or bacteria

Most extremophiles are bacteria or archaea because these microorganisms have simpler cellular structures and can adapt more quickly to extreme environments. Bacteria and archaea are both prokaryotes, meaning they lack a true nucleus and other membrane-bound organelles. This simplicity allows them to have a more flexible metabolism and adapt more quickly to changing environmental conditions.

In addition, many extremophilic bacteria and archaea have specialized adaptations, such as specialized enzymes and cell membranes, that allow them to thrive in extreme environments. These adaptations can include heat-shock proteins, membrane lipids with unusual structures, and enzymes that can function in the presence of high salt concentrations or extreme pH levels.

In contrast, eukaryotic organisms, such as plants, animals, and fungi, have more complex cellular structures and are generally less adaptable to extreme environments. They also tend to have a more specialized metabolism that may not be able to function in extreme conditions.

However, there are some eukaryotic extremophiles, such as certain types of algae and fungi, that are able to survive in extreme environments. These organisms often have specialized adaptations, such as heat-shock proteins and unique metabolic pathways, that allow them to thrive in harsh conditions.

Question 3

What is an extremophiles called that can survive in high pH?

Answer 3

Alkaliphiles

Question 4

What is an extremophiles that can live in low pH?

Answer 4

Acidophiles

Question 5

What is an extremophiles called that can live in high temps?

Answer 5

Thermophiles

Question 6

What is an extremophiles called that can survive in low temps?

Answer 6

Psychrophiles

Question 7

What is the name of an extremophiles that can survive in high salinity?

Answer 7

Halophiles

Question 8

What is the name of an extremophile that can survive low water/desiccation?

Answer 8

Xerophiles

Question 9

What happens if they dont “love” their environment (Phillic)

Answer 9

Some organisms may ‘tolerate’ their environment

Eg. Thermotolerant bacteria

Question 10

Defining extremes for different environments:

Answer 10

Limiting conditions (tolerating to thriving)

High pH = 8-12.5

Low Ph = 0.7-4

High temps = 50-80

Low temps = <15

High salinity = 15-37.5% NaCl

Low water/desiccation - anhydrobiotic

Question 11

What are humans?

Answer 11

Mesophiles

= A mesophile is an organism that thrives at moderate temperatures, typically in the range of 20-45°C (68-113°F). Mesophiles are the most common type of organisms and include many types of bacteria, archaea, and eukaryotic organisms, including humans.

Question 12

What temperatures can multi and single cellular eukaryotes survive?

Answer 12

Multi cellular eukaryotes can survive <50 degrees Celsius.

Single cellular eukaryotes can survive <60 degrees Celsius.

Question 13

What are hyperthermophiles?

Answer 13

They can survive between 80-115 degrees Celsius and can be found in hot springs and ocean vents.

(Methanogen methanopyrus is an example and typically thrives at temps of 84-110 but some can survive and reproduce at 122 C)

Question 14

How do hyper/ Thermophiles adapt to extreme temperatures?

Answer 14

High temperatures can cause denaturation of DNA and proteins in most organisms. However, hyperthermophilic and thermophilic organisms have evolved specialized mechanisms to prevent or repair such damage and maintain their cellular functions even at high temperatures.

• In terms of DNA, hyperthermophilic and thermophilic organisms have evolved specific DNA-binding proteins that help to stabilize DNA structure at high temperatures.
• They have a higher proportion of G-C nucleobasis that are more stable at higher temps
• They have a changed composition to reduce membrane fluidity and retain integrity.

Regarding proteins, hyperthermophilic and thermophilic organisms have enzymes that are more stable and active at high temperatures than those found in mesophilic organisms. These enzymes are able to function properly even at high temperatures, and some have evolved to maintain their structure through the formation of more extensive intermolecular bonds or disulfide bridges.

Question 15

Was earths earliest life Thermophilic?

Answer 15

Some researchers have suggested that the earliest life forms may have been adapted to high temperatures, given that the early Earth was a much hotter and more hostile environment than it is today.

• Some of the microbes nearest the roots of the tree of life could survive high temps and so would have been closely related to LUCA , suggesting LUCA was a Thermophile

One theory is that the first life forms on Earth may have been hyperthermophilic, able to survive in environments with temperatures exceeding 100 degrees Celsius. This idea is based on the fact that the earliest evidence of life on Earth, in the form of fossilized microorganisms known as stromatolites, dates back to around 3.5 billion years ago, a time when the Earth’s surface was believed to have been constantly bombarded by intense heat and radiation from the sun.

However, other researchers have argued that the earliest life forms on Earth were more likely to have been mesophilic, adapted to moderate temperatures, and that the ability to survive at high temperatures may have evolved later as a response to changing environmental conditions.

In conclusion, while it is still unclear whether the earliest life on Earth was thermophilic or not, ongoing research and investigation may provide new insights into the origins of life on our planet.

Question 16

What are psychrophiles?

Answer 16

Psychrophiles are a group of microorganisms that are adapted to thrive in cold temperatures, typically between -15°C to 10°C, and are often found in polar regions or deep ocean waters. They have evolved a range of specialized mechanisms that allow them to maintain their cellular functions in these extreme environments.

The lowest temps recorded for microbial communities are -18 C eg at the Himalayan ridge

Water is the universal solvent for life and so if intracellular water freezes at such cold/low temps then it is game over. There are ways that have been adapted to avoid this!

Question 17

How have psychrophiles adapted to survive cold temps?

Answer 17

They have had to change their proportions of unsaturated fatty acids to increase their flexibility.

Specialised enzymes have a more flexible and open structure, which allows them to be more active at cold temperatures.

They have developed antifreeze proteins that help to prevent the formation of ice crystals within the cell, which can damage cellular structures.

They have increased their concentration of salts and sugars to reduce the freezing point of water.

They depress the freezing point of intercellular water and/or protects cells during thawing.

Question 18

Are there upper and lower temperature limits for life?

Answer 18

Upper limit = of 140-150 C
Above this temperature proteins and DNA denature, preventing reproduction

Lower limit = of -60 C
Even with antifreeze proteins, microbes struggle to reproduce at this temperature.

Question 19

What is the theoretical limit between -40 and 150 C

Answer 19

The theoretical limit between -40 and 150 is most likely referring to the temperature range that is considered safe for human survival. This range is often referred to as the “human comfort range” or the “thermal comfort zone.”

Temperatures outside of this range can be uncomfortable, dangerous, or even life-threatening. When temperatures fall below -40 degrees Celsius (-40 degrees Fahrenheit), the risk of hypothermia and frostbite increases, and it becomes difficult for the body to maintain a normal internal temperature. Similarly, when temperatures rise above 150 degrees Fahrenheit (65 degrees Celsius), the risk of heat exhaustion and heat stroke increases, which can be fatal.

Question 20

What are halophiles?

Answer 20

Halophiles are microorganisms that are adapted to live in high-salt environments, such as salt lakes and saline soils. These organisms have developed unique adaptations that allow them to survive and thrive in these extreme conditions, including adaptations that can contribute to the biological pump.

Question 21

Halophile adaptions for the Na+ and K+ biological pump?

Answer 21

These organisms have developed unique adaptations that allow them to survive and thrive in these extreme conditions, including adaptations that can contribute to the Na and K biological pump.

• Enzyme pushes sodium out and pulls in potassium to stabilise the membrane and stop water from escaping
• Uses the Na+/K+ ATPase enzyme to push Na and K in and out of the cell
• Pushes out 3 ions of Na+, pulls in 2 ions of K+
• Stabalises the cell membrane, controls pressure and keeps from escaping

The Na and K biological pump is the process by which living cells maintain a balance of sodium (Na+) and potassium (K+) ions across their membranes. This is important for a number of cellular processes, including the generation of electrical signals and the uptake of nutrients.

Halophiles have developed adaptations that allow them to maintain a balance of Na+ and K+ ions in their cells, despite the high-salt environment in which they live. One adaptation is the use of specific ion pumps and channels that selectively transport Na+ and K+ ions across their membranes. These pumps and channels are able to maintain the ion gradient necessary for normal cellular function, even in the presence of high levels of salt.

In addition, some halophiles are able to accumulate large amounts of compatible solutes, which are organic compounds that help to balance the osmotic pressure inside and outside of the cell. These compatible solutes can include molecules such as glycine betaine, proline, and ectoine, and they allow halophiles to survive and thrive in high-salt environments by preventing water loss and maintaining cellular function.

Overall, the adaptations that halophiles have developed to maintain a balance of Na+ and K+ ions in their cells can contribute to the Na and K biological pump by regulating cellular processes and allowing these microorganisms to thrive in high-salt environments. This has important implications for understanding the evolution and ecology of microorganisms in extreme environments, as well as for biotechnology applications such as the production of salt-tolerant crops and the development of novel antibiotics.

Question 22

What is a Halophile adaption?

Answer 22

They have osmoprotectants or compatible solutes that help them survive and thrive in high-salt environments. Halophiles are microorganisms that have evolved specialized mechanisms to adapt to the high-salt conditions, including the accumulation of compatible solutes.

The solutes are such as amino acids and sugars, and amino acid derivatives betaines and ectoine. They have neutral charge and low toxicity which accumulate so that salt and Na+ ions are excluded.

Most metabolic energy goes into maintain intra-cell environment. Upper salinity limits means the organism can survive is reliant on metabolic efficiency.

Question 23

Do halophiles have osmoprotectants?

Answer 23

halophiles have osmoprotectants or compatible solutes that help them survive and thrive in high-salt environments. Halophiles are microorganisms that have evolved specialized mechanisms to adapt to the high-salt conditions, including the accumulation of compatible solutes.

Question 24

What are halotolerant organisms?

Answer 24

Halotolerant organisms are those that are able to tolerate moderate levels of salt in their environment, but are not adapted to thrive in high-salt environments like halophiles.

Eg. Shark bay is known for its high salt concentration and diverse range of microorganisms, including halophiles. The area has been extensively studied for its microbial communities, including halophilic archaea and bacteria, and there have been several reports of novel species and strains discovered in this region.

Question 25

What are Chemotroph acidophiles?

Answer 25

Chemotroph acidophiles are a group of microorganisms that are adapted to thrive in acidic environments and obtain their energy from chemical reactions, rather than from photosynthesis. They can be found in a wide range of habitats, including acidic mine drainage, hot springs, and geothermal vents.

One of the key adaptations of chemotroph acidophiles is their ability to tolerate high levels of acidity. They are able to maintain a stable internal pH by using specialized membrane transporters to export excess protons from the cell. Additionally, they produce enzymes that are active at low pH, allowing them to carry out key metabolic reactions even in highly acidic environments.

Chemotroph acidophiles obtain their energy from a variety of chemical reactions, such as the oxidation of sulfur compounds or iron. Some acidophiles are able to use sulfur compounds, such as sulfuric acid or elemental sulfur, as an energy source, while others can oxidize iron or other metals. In some cases, acidophiles can also use organic compounds as an energy source, such as in the case of acidophilic bacteria that are able to degrade aromatic hydrocarbons in acidic environments.

The ability of chemotroph acidophiles to thrive in extreme and highly acidic environments has important implications for biotechnology and industrial applications, such as the bioleaching of metals from ores or the treatment of acidic wastewater. Additionally, acidophiles play important ecological roles in natural environments, such as in the cycling of sulfur and other elements.

Question 26

What reactions are most efficient at a low pH?

Answer 26

Iron reduction and oxidation

Fe2+ is soluble at low pH or under anaerobic conditions

Otherwise it is oxidised to ferric iron (Fe3+) which becomes insoluble oxides that drop out of solution.

Question 27

Iron reduction

Answer 27

• During iron reduction, ferric iron (Fe3+) is the electron acceptor, generally H2 , S or organic carbon (heterotrophy) is the electron donor and becomes oxidises whilst iron is being produced.

Chemotroph acidophiles are able to obtain energy from the oxidation of inorganic compounds, such as sulfur or iron, through a process known as chemolithotrophy. In this process, the microorganisms use specialized enzymes to catalyze the transfer of electrons from the inorganic compound to a terminal electron acceptor, such as oxygen or nitrate, resulting in the generation of energy.

The oxidation of inorganic compounds also leads to the production of protons and a decrease in pH, resulting in the acidic conditions that are characteristic of many acidophilic environments. Acidophilic microorganisms are able to tolerate these conditions by using specialized transporters to export excess protons from the cell, and by producing enzymes that are active at low pH.

In addition to oxidation reactions, chemotroph acidophiles are also capable of carrying out reduction reactions. For example, some acidophilic microorganisms are able to reduce sulfur compounds, such as sulfite or elemental sulfur, to hydrogen sulfide, which can then be oxidized for energy. Other acidophilic microorganisms are able to reduce iron or other metals, using them as electron acceptors in a process known as anaerobic respiration.

Overall, the ability of chemotroph acidophiles to carry out both oxidation and reduction reactions allows them to obtain energy from a wide range of inorganic compounds and to thrive in the extreme and often toxic conditions of acidic environments.

Question 28

Sulphur oxidation and sulphate reduction

Answer 28

S + O2 + H2O —> H2SO3 + 0.502 —> H2SO4
Elemental sulphur

H2SO + 2O2 —> 2H+ + 8e-
Hydrogen sulphide

• In anaerobic environments, nitrate NO3, iron and organic carbon can be used as the electron acceptor

Sulfur is a commonly used electron donor and acceptor by microorganisms, which can carry out both oxidation and reduction reactions involving sulfur compounds.

Sulfur oxidation is the process by which microorganisms oxidize sulfur compounds such as sulfide, elemental sulfur or thiosulfate to obtain energy. This process involves the transfer of electrons from the sulfur compound to a terminal electron acceptor, such as oxygen or nitrate, through specialized enzymes known as sulfur oxidases. The oxidation of sulfur compounds results in the release of energy that can be used by the microorganisms to fuel their metabolism.

Sulfur reduction, on the other hand, is the process by which microorganisms use sulfur compounds as electron acceptors. This process involves the transfer of electrons from a donor compound, such as organic matter or hydrogen gas, to the sulfur compound, through specialized enzymes known as sulfur reductases. The reduction of sulfur compounds results in the production of hydrogen sulfide or other reduced sulfur compounds, which can then be used by the microorganisms as a source of energy.

Sulfur-oxidizing and sulfur-reducing microorganisms play important roles in biogeochemical cycles, such as the sulfur cycle, and can have significant impacts on the environment

Question 29

What are the acido/alkaliphile adaptions for the Biological H+ proton pump?

Answer 29

In acidophiles, the biological H+ pump is used to maintain a neutral cytoplasmic pH in the presence of an acidic environment. The pump actively transports H+ ions out of the cell, thereby preventing the accumulation of excess H+ ions in the cytoplasm. This is essential because an acidic environment can cause damage to cellular structures and interfere with cellular metabolism.

In alkaliphiles, the biological H+ pump works in the opposite way. The pump actively transports H+ ions into the cell, thereby maintaining a neutral cytoplasmic pH in the presence of an alkaline environment. This is necessary because an alkaline environment can also cause damage to cellular structures and interfere with cellular metabolism.

(Pumps protons into lower pH whilst maintaining suitable pH within)

Both acidophiles and alkaliphiles have adapted their biological H+ pumps to function optimally at their respective pH ranges. For example, acidophiles have H+ pumps that are more efficient at pumping out H+ ions in acidic environments, while alkaliphiles have H+ pumps that are more efficient at pumping in H+ ions in alkaline environments. These adaptations help to ensure that the microorganisms are able to maintain a neutral cytoplasmic pH and survive in their extreme environments.

Question 30

Can organisms thrive in multiple extremes?

Answer 30

Many organisms have adapted to thrive in environments with multiple extremes.

Eg.
- Acidophiles are typically also thermophilic (hot springs)
- Halophiles are typically also alkaliphiles (soda lakes)

Very commonly get poly extremophiles= many environments have different extremes and so there are different extremophiles

Question 31

Why are extremophiles important for astrobiology?

Answer 31

Extremophiles are important for astrobiology because they provide insights into the types of life that may exist in extreme environments beyond Earth. Astrobiology is the study of the origin, distribution, and evolution of life in the universe, and one of the key questions in astrobiology is whether life exists elsewhere in the universe.

• They help us define the boundaries of life
• Can help predict theoretical limits for life to exist on other planets

Extremophiles have demonstrated that life can survive and even thrive in conditions that were once thought to be inhospitable to life. For example, organisms have been found living in highly acidic environments, in the depths of the ocean where there is no sunlight, and in environments with high levels of radiation. The study of extremophiles has led to the discovery of novel biochemical pathways, enzymes, and molecules that may have applications in biotechnology, medicine, and environmental remediation.

Astrobiologists are interested in extremophiles because they provide a framework for thinking about the conditions that may be suitable for life beyond Earth. By studying extremophiles, astrobiologists can identify potential habitats for life elsewhere in the universe, such as subsurface oceans on icy moons or on the surface of Mars. Extremophiles also provide a basis for understanding how life may have originated on Earth and how it may have adapted to different environments throughout the planet’s history.

In summary, extremophiles are important for astrobiology because they expand our understanding of the conditions that may support life beyond Earth and provide a basis for thinking about the search for life elsewhere in the universe.

Question 32

Where could extremophiles such as on earth live in other planets/moons in the universe?

Answer 32

Acidic hot springs on mars could have extremophiles like earth.

There are cold and salty sub-surface oceans on europa.

Question 33

Is titan too extreme for life?

Answer 33

There is a tropical average of -180 C

itan, a moon of Saturn, is one of the most extreme environments in our solar system, with temperatures averaging around -180 C and an atmosphere composed mostly of nitrogen with some methane and other hydrocarbons. The surface of Titan is also covered in a thick layer of organic compounds, which could be a potential source of energy for life.

While the conditions on Titan are certainly challenging for life as we know it, it is not impossible that some form of life could exist there. In fact, some scientists have speculated that life could exist in the subsurface ocean that is believed to exist beneath the icy crust of Titan. This ocean is thought to be composed of water and ammonia and could potentially provide a more habitable environment for life.

However, as of yet, there is no direct evidence of life on Titan, and further exploration and study of this moon will be needed to determine if it is truly too extreme for life as we know it.

Question 34

Could extremophiles survive on titan?

Answer 34

It is possible that extremophiles could live on Titan, but there are several factors that make it unlikely.

Titan is the largest moon of Saturn and is known for its cold, methane-rich atmosphere and surface. The temperatures on Titan are extremely cold, with an average temperature of -290 degrees Fahrenheit (-179 degrees Celsius). Additionally, the atmosphere on Titan is primarily composed of nitrogen and methane, with only trace amounts of oxygen and other elements necessary for life.

However, there are some extremophiles on Earth that are adapted to cold temperatures and can survive in environments with limited oxygen and nutrients. For example, certain species of bacteria and archaea can survive in sub-zero temperatures in the Antarctic, and some organisms are capable of living in extreme environments such as hydrothermal vents on the ocean floor.

Despite this, it is unlikely that extremophiles could survive on Titan because of the extreme cold and lack of nutrients. The methane-rich atmosphere and surface of Titan also make it difficult for life as we know it to exist, as methane is toxic to most organisms on Earth.

Question 35

Can extremophiles provide an upper and lower constraint on the limits of life?

Answer 35

Yes, extremophiles can provide both an upper and lower constraint on life. By studying extremophiles, we can learn about the limits of habitability on Earth and gain insights into the potential for life to exist in extreme environments elsewhere in the universe.

Extremophiles that thrive in high temperatures, for example, can give us information about the upper limit of temperature at which life can survive. Similarly, extremophiles that survive in extreme cold or dry conditions can give us insights into the lower limits of temperature and water availability for life.

By understanding the mechanisms by which extremophiles are able to survive in such extreme conditions, scientists can also gain insights into how life might adapt to different environments on other planets and moons. This knowledge can be used to guide the search for life beyond Earth, by helping to identify the most promising environments where life could potentially exist.