Life at the extremes
Evolution struggles to explain the existence of extremophiles (e.g. the tardigrades)
Posted on homepage: 27 March 2013 (GMT+10)
Could anything live in a boiling mudhole? Actually, in recent years, many new species have been discovered in many places which were thought to be far too inhospitable to support life.
Not just in boiling mud, but in steaming volcanic craters, in the rocky chimneys that grow above deep-ocean volcanic vents spewing forth hot salty water (‘black smokers’), in areas of extreme cold in the Antarctic, and even in the hyper-salty Dead Sea in Israel, a treasure trove of living organisms has been revealed. These ‘extremophiles’ (Greek -philos = ‘loving’) can tolerate astonishing extremes of temperature, acidity, pressure, dryness and salinity.1,2,3,4
For example, Sulfolobus solfataricus can survive to 88ºC (190ºF) near fuming sulfurous volcanic vents (see photo in Creation magazine p. 42). Pyrococcus furiosus (‘furious fireball’) tolerates 100ºC (212ºF). Even more amazing is Pyrolobus fumarii, which lives within the walls of black smokers, and which not only survives, but can actually grow at temperatures up to 113ºC (235ºF).5 Ferroplasma acidarmanus thrives in acid mine drainage (pH0)6 in California—a brew of sulfuric acid and high levels of arsenic, cadmium and other toxic chemicals.
Although most of these new species are only tiny microbes, the impact of their discovery has been huge, and the study of extremophiles is now virtually a whole new branch of science in its own right.7
- It has led to ‘the recent upheaval in the way we classify organisms’, as scientists categorized many of the new-found single-celled organisms into ‘a new branch of life’, the Archaea, which they elevated to the overarching rank of domain.8,9,10
- After the initial discovery of life in the black smokers, further study of such areas revealed not only other extremophiles, but also new information about life in the broader ocean, in less harsh environments.11
- Industry is copying aspects of the internal chemistry ‘survival kits’ of extremophiles for use in situations where standard processes break down. E.g. the enzymes of heat-loving organisms are used in DNA fingerprinting and baking processes. Those of cold-tolerant ones are used in maturing cheese, and ‘pasteurizing’ foods while keeping them chilled to thwart the growth of undesirable bacteria. Alkali-tolerant enzymes are used to lighten and soften the fabric of jeans, giving a ‘stonewashed’ effect without having to use actual stones or similar particles to abrade the fabric.
- The discovery that life can exist in extreme environments has raised evolutionists’ hopes that it could exist elsewhere in the universe, prompting ‘astrobiologists’ and others to call for increased effort to be put into the search for extraterrestrial life.12,13
Despite such evolutionary enthusiasm,14extremophiles in fact raise new difficulties for evolutionists. How does one explain how organisms could have evolved to survive in such specialized extreme environments as deep-sea rock chimneys, through which superheated solution as hot as 350ºC (660ºF) erupts? Some evolutionists say that it was in just such circumstances that life on this planet first appeared—in the hot, low-oxygen environment of the early oceans, bathed in the mineral-rich fluids gushing from hydrothermal vents. Thus, the Archaea ‘pursue their peculiar lifestyles in the more extreme environments of Earth, as they may have done for perhaps 3.5 billion years.’9 But none other than the father of modern ‘origin of life’ experiments, Stanley Miller, pointed out that life’s ‘building blocks’ are too unstable for a hot beginning of life.15
In any case, the notion of remnant life-forms from billions of years ago is not so easily applied to other extremophiles, such as those that live in the polar ice caps, in hyper-saline or acidic environments, in parched desert environments or even the super-frigid wastes of dry Antarctic valleys. And even more telling is the fact that some extremophiles are known to be able to withstand physical extremes beyond anything present in the natural environment.
For example, the bacterium Deinococcus radiodurans (‘radiation-resistant weird-ball’) has been identified in cans of meat that had been sterilized (or so it was thought) with gamma radiation. While a thousand ‘rads’ of ionizing radiation is enough to kill a person, this bacterium can survive 12 million rads!
According to the theory of evolution, an organism will possess only the attributes it needs to survive. So where did Deinococcus live that it had to withstand 12 million rads of gamma radiation? Natural radiation on Earth is nowhere more than a small fraction of this level. The best ‘answer’ that evolutionists can suggest is that the bacterium evolved to withstand extreme dryness, and so radiation resistance is just a fortuitous consequence of that evolutionary process.16
For Christians who believe the Bible, the ability of life to ‘conquer’ and inhabit extreme environments ought not to be too surprising, as the Lord intended for living things to ‘fill’ the whole Earth (Genesis 1:28). And when we consider other examples of how God’s creatures have indeed spread out to occupy the harshest environments upon the Earth, the evolutionists’ arguments break down even further.
Worms of ‘fire’, worms of ‘ice’
For it is not just ‘primitive’ single-celled organisms that live in these harsh environments, but multicellular creatures as well. For example, the ‘Pompeii worm’ (Alvinella pompejana) lives in papery tubes that it builds on the sides of the black smokers mentioned earlier. The temperature inside these tubes has been measured at 85ºC (185ºF), and there is even a report of one worm which left its tube and curled itself around the researchers’ temperature probe, showing 105ºC (221ºF)!17
And another newly discovered species of worm, Hesiocaeca methanicola, has been found living on the seafloor in the Gulf of Mexico—the only animal known to colonize methane hydrate ‘ice’. This crystalline mixture of water, methane and other hydrocarbons freezes into a solid only under high pressures and relatively low temperaturess—surely one of the most specialized environments in the world.18
The worms were observed at a depth of 700 m (2,300 ft) and 6ºC (43ºF), where methane hydrate is at the limit of its stability, so even a tiny increase in temperature will see the worms’ home disappear in an explosion of bubbles. Though methane ice is as hard as rock, its tendency at this temperature and depth to fizzle into gas appears to offer the worms the opportunity they need to set up a colony. By wafting its tiny pink paddle-like ‘feet’, a worm is able to slowly use the resulting current of water to burrow into the ice. But isn’t that a lot of effort to go to, just for a home? As one researcher commented, ‘Why worms spurn the good life in the mud for a life on ice is a puzzle.’17
The almost-invincible tardigrades
But of all the organisms so far identified to be able to live in harsh environments, the toughest animals on Earth by far are the ‘tardigrades’. You can freeze them, boil them, dry them, starve them and even put them in a vacuum—yet they still bounce back.
The form of these little creatures (mostly less than 1 mm (one twenty-fifth of an inch) long) has earned them the nicknames of ‘moss piglets’, ‘bear animalcules’ and ‘water bears’. With their stumpy legs, tiny claws and slow, lumbering gait they really do look like a microscopic bear.19 Around 700 species of tardigrades have been found in habitats ranging from the freezing peaks of the Himalayas to the hottest, driest deserts, right down to the deepest ocean trenches of the Pacific.
Slow down, turn off … revive, survive!
How do they withstand such environmental extremes? By shutting down their metabolism during unfavourable conditions. When things become unbearably hot, or cold, or dry, e.g., many tardigrades curl in their head and legs and roll up into a barrel-like shape called a ‘tun’.20 They then make the biochemical preparations for shutting everything down—even their respiration ceases completely. But later, when favourable circumstances return, the tardigrade uncurls itself, again extending its legs and head, and life goes on as before.
The (known) record duration for survival (in this case, without water) is 120 years, for tardigrades taken from dried-out moss kept in a museum in Italy.21
And biologists are amazed at the sort of laboratory treatment that tardigrades can endure—often far worse than any conditions they would ever experience on Earth. For example, they have revived after having been frozen in liquid helium (-272ºC, or -458ºF), just a fraction above absolute zero (-273.15ºC, or -459.67ºF), the lowest temperature possible.22,23 At the other extreme, they have survived being heated to 151ºC (304ºF). They have survived being zapped with X-rays with an intensity 250 times stronger than that which would kill a human. Tardigrades can even survive being photographed by an electron microscope, which requires putting them in a vacuum and bombarding them with electrons.
Bearing up under pressure
At least two species of tardigrades (Macrobiotus occidentalis (order Eutardigrada) and Echiniscus japonicus (Heterotardigrada) have been shown to be able to survive extraordinarily highhydrostatic pressures, 600 MPa (6,000 atmospheres), i.e. six times greater than the pressure at the bottom of the deepest ocean on Earth.24,25 To put this in context, research has shown that when other animals are exposed to high pressures, their cell membranes, proteins and DNA are damaged. In most micro-organisms, growth and metabolism stops at pressures of around 30 MPa (300 atmospheres), and even among the microbes which are resilient to high pressures, most will die at 300 MPa (3,000 atmospheres). In addition, while there are organisms (other than tardigrades) that can survive very high pressures, a sudden change can be lethal to them—a danger to which human divers must be ever alert.26 But tardigrades not only can survive extended periods at 600 MPa (6,000 atmospheres!), but high-speed decompression as well.
As creationists have pointed out before, the ability of tardigrades to survive being subjected to such extreme laboratory treatments (radiation, cold temperature, hydrostatic pressure), far more severe than any Earth environment, poses a very clear difficulty for evolutionary theory.27 As one scientific writer put it, ‘With such an arsenal of adaptations for survival, tardigrades appear to be over-engineered.’21
And, not just tardigrades—as this latest surge of exploration and laboratory research reveals yet more extremophile microbes and other organisms able to withstand far harsher conditions than anywhere on Earth, the challenge to evolutionary theory becomes even more intractable. This is because natural selection can only select characteristics necessary for immediate survival. Consequently, evolution cannot be expected to ‘overequip’ creatures for a host of environments they have never faced.
For Christians, though, the ‘over-design’ of these creatures speaks of a Designer (Romans 1:20), and it is not surprising that God also built into the living things of His creation the capacity to move out and ‘fill’ the whole world, just as He had commanded (Genesis 1). And so indeed, we see today that living things inhabit the harshest environments from ocean to mountaintop and from pole to pole—even at the very extremities of the Earth. Just as the Lord (who knew, incidentally, prior to Creation, of the coming effects of the Curse and the later Flood on future environments) intended for them to do.
Just how do they do it?
How do extremophiles manage to thrive in conditions that are fatal to other organisms? Researchers are slowly gaining some insights into their various survival mechanisms:
- Keeping the external environment out. E.g. Cyanidium caldarium and Dunaliella acidophila live in acidic environments (pH 0.5), while inside the cell remains near-neutral (approx. pH 7).1 (Of course, the protective molecules of their external ‘skin’ must be acid-tolerant.) This strategy requires functional machinery that can quickly remove the ‘problem’; heavy-metal-resistant bacteria use an efflux pump to remove zinc, copper and cobalt before internal levels become toxic.
- Special enzymes. Dubbed ‘extremozymes’, they often resemble standard enzymes in structure but contain more strong bonds (e.g. ionic and covalent bonds).2
- Stabilized DNA. Extremophiles’ higher ratio of G–C to A–T linkages and the presence of MgCl2 and KCl salts stabilize the DNA at high (>70°C) temperatures.1
- Salty cells. Organisms living in a salty environment (e.g. Halobacterium salinarum) ensure their internal cell solution is even ‘saltier’ (using, e.g., KCl or glycine betaine), thus retaining water rather than losing it.
- Rapid repair of DNA. The incredible radiation tolerance of Deinococcus radiodurans may stem from its highly efficient DNA repair system. It not only has at least three ‘backup copies’ of its full DNA sequence (genome), but also limits mutations by removing damaged DNA from the cell before it can be reincorporated.3
- Special sugar. When tardigrades facing dry conditions enter the tun state, levels of a sugar called ‘trehalose’ increase rapidly. Researchers suggest that trehalose substitutes for water molecules, thus maintaining membrane fluidity and protecting vital cell components.4 This inspired Japanese experiments with trehalose for transplant organ storage (rat hearts were successfully revived after 10 days).5 (See also Long-life blood platelets.)
Scientists are still trying to decipher the chemical processes involved and how they confer such spectacular resistance to extremes. The idea that such complex and incredibly fine-tuned mechanisms could be the result of evolution defies logic.
Neither the modern identification of human genetic diseases nor the use of DNA evidence in law courts would have been realized if the Master Designer’s handiwork had not been available for study—for DNA sequencing only became possible with the discovery of the extremozymes in such super-heat-loving bacteria.
- Rothschild, L.J. and Mancinelli, R.L., Life in extreme environments, Nature 409(6823):1092–1101, 2001.
- Madigan, M.T. and Marrs, B.L., Extremophiles, Scientific American 276(4):66–71, 1997.
- White, O. et al., Genome Sequence of the Radioresistant Bacterium Deinococcus radiodurans R1, Science 286(5444):1571–1577, 1999.
- Copley, J., Indestructible, New Scientist 164(2209):45–46, 1999.
- Copley, J., Putting life on hold: Weird creatures have some cute lessons for organ transplanters, New Scientist 160(2159): 7, 1998.
References and notes
- Some extremophiles have been known for more than a century, but the search for them has intensified during the past decade, as scientists have recognized that places once assumed to be sterile in fact abound with life. Return to text.
- Madigan, M.T. and Marrs, B.L., Extremophiles, Scientific American 276(4):66–71, 1997. Return to text.
- Rothschild, L.J. and Mancinelli, R.L., Life in extreme environments, Nature 409(6823): 1092–1101, 2001. Return to text.
- Cossins, A.R., Some like it hot, Nature 393(6682):227–228, 1998. Return to text.
- Although pure water boils at sea level at 100ºC (212ºF), the boiling point of water increases with pressure, so water at the bottom of the ocean remains liquid even if heated to 400ºC (750ºF). Return to text.
- pH 0 signifies extremely strong and concentrated acid, more so than the strongest battery acid. By way of contrast, a ‘neutral’ solution which is neither acidic nor alkaline, such as pure water, would have pH 7. Return to text.
- As indicated by the increasing number of scientific conferences, the launch of specific public agency funding programs, and research effort by biotechnology industry. Return to text.
- Smith, D.C., Expansion of the Marine Archaea, Science 293(5527):56–57, 2001. Return to text.
- Willmer, P.G., Extremophiles in the raw, Nature 408(6814):771, 2000. Return to text.
- Molecular studies have revealed the inadequacy of the ‘traditional’ system of five (or more) kingdoms. Scientists have instituted a parallel system with three overarching ‘domains’: Eukaryota (plants, humans and animals, all with cells containing a nucleus), Bacteria (cells have no nucleus) and Archaea (similar to bacteria in that cells have no nucleus, but are biochemically and genetically distinct). Return to text.
- E.g. archaeans have been found to inhabit less extreme environments as well. The Archaea constitute about 20% of the total marine picoplankton biomass worldwide. They have also been found in freshwater lakes and terrestrial soils. Ref. 8. Return to text.
- Bortman, H. and Ball, P., News meeting report [of the First Astrobiology Science Conference in California]: Storming the Tower of Babel, Nature 404(6779):700, 2000. Return to text.
- Brownlee, D., Who is out there? Nature 411(6841):994–995, 2001. Return to text.
- One of the difficulties for evolutionists is insufficient time to have the Earth supposedly cool enough (after the alleged ‘big bang’) for life to have arisen ‘by chance’. Consequently, they are eager to find evidence that life began to evolve in (supposedly) older areas of the universe, and was later transported to Earth. See Grigg, R., Did life come from outer space? Creation 22(4):40–43, 2000. Return to text.
- Miller, S. and Lazcano, A., The origin of life—did it occur at high temperatures? Journal of Molecular Evolution 41:689–692, 1995 (reported in Creation 20(1):9, 1997). Return to text.
- Travis, J., Meet the Superbug, Science News 154(24):376–378, 1998. Return to text.
- Pain, S., Extreme worms, New Scientist 159(2144):48–50, 1998. Return to text.
- This also provides support for the Biblical Flood/Ice Age model—see Silvestru, E., Bubbles of surprise, TJ 15(2):89–95, 2001. Return to text.
- Italian scientist Lazzaro Spallanzani named them ‘tardigrades’ in 1776 for their ponderous walk (Lat. tardus = sluggish, gradus = walk). Return to text.
- Not all tardigrade species share the same abilities. For example, marine tardigrades do not form the tun state, and cannot survive drying out. Return to text.
- Copley, J., Indestructible, New Scientist 164(2209):45–46, 1999. Return to text.
- The damage to animal tissue during freezing is caused as ice crystals grow and damage cell membranes. Researchers have identified large proteins in an Arctic tardigrade that raise the freezing point of these animals compared to others. Tardigrades would therefore freeze more quickly, but with lots of tiny crystals that are less likely to cause damage than larger crystals—thus enabling these animals to survive being frozen. Return to text.
- Note that (i) unlike other elements, helium will never freeze except under artificially-applied high pressure, and (ii) no place in the universe is naturally at such a low temperature. See Sarfati, J., Blowing old-Earth belief away, Creation 20(3):19–21, 1998. Return to text.
- The Mariana trench (11º 22' N, 142º 25' E) is the world’s deepest seafloor at 10,898 m (35,755 ft). Atmospheric pressure at sea level is approximately 0.1 MPa (actually 101.35 kPa, or 1 atmosphere). Under the water, pressure increases at a rate of around 10.5 MPa (103.6 atmospheres) per 1,000 m (about 3,300 ft) depth. Return to text.
- Seki, K. and Toyoshima, M., Preserving tardigrades under pressure, Nature 395(6705): 853–854, 1998. Return to text.
- The ‘bends’ is caused by nitrogen bubbles forming in the diver’s blood and fatty compounds in the nervous system if the pressure drops too quickly as the diver resurfaces. Return to text.
- Vetter, J., The ‘little bears’ that evolutionary theory can’t bear!, Creation 12(2):16–18, 1990. Return to text.