In remote eastern Siberia, hundreds of active volcanoes rise above a rocky landscape dotted with thousands of bubbling hot springs.
Russians call the region the ‘land in the making’ because of the rate at which the volcanoes churn out molten rock. That new ‘land’ of the Kamchatka Peninsula is one of the most inhospitable regions on any of Earth’s continents.
But it is not lifeless. In the hot, toxic water of those bubbling springs lurk all manner of strange microbes – some even content to live in water just a shade below 100C.
More of these “extremophiles” are coming to light every few years. This is good news, not just for the scientists who study them, but also for a variety of industrial processes.
Kamchatka is so remote that it takes more than nine hours to fly there from Moscow. It is one of the most volcanically active places on Earth and forms part of the Pacific “Ring of Fire”.
In the hot, toxic water of those bubbling springs lurk all manner of strange microbes
To truly experience the beauty of the region – a UNESCO World Heritage site – you must travel by helicopter. Few scientists have made the journey.
Elizaveta Bonch-Osmolovskaya of the Russian Academy of Sciences, Moscow, has been visiting Kamchatka regularly since 1982. Most of her expeditions have been to the Uzon Caldera, a region in Kronotsky National Park that formed when a volcano collapsed 200,000 years ago.
The caldera is now like a bowl ringed by mountains, and it is filled with hundreds of hot springs, geysers and mud pots strewn across five thermal fields and heated by tumultuous geothermal activity deep in the bowels of the Earth.
The rock is rich in arsenic, phosphorus, copper, lead, antimony, and even gold. Geothermal gases, including methane, hydrogen sulphide, nitrogen and carbon dioxide leak out to the Earth’s surface, or bubble up in hot springs.
The place is very dangerous: you can easily fall into the boiling clay or inhale poisonous fumes. But for many microbes this is home – and for biologists who study such extremophiles, Uzon is a perfect place to work.
Most organisms could not survive in the hot springs
The journey to Uzon, by helicopter, takes two hours. “There are no roads,” says Bonch-Osmolovskaya. “Each time we stayed there for one or two weeks, and of course we had to bring everything with us – food, fuel for cooking, laboratory equipment. At first there were two wooden houses for us to stay in, but then they were destroyed and we all lived in tents. Now there is a house again where people can live and work.”
In September 2005, 20 Russian and US scientists travelled together to the Uzon Caldera for a five-year Joint Russian-American expedition headed by Juergen Wiegel from the University of Georgia. Researchers constructed the Kamchatka Microbial Observatory, a natural laboratory for studying extremophiles.
Most organisms could not survive in the hot springs, says Frank Robb at the University of Maryland in Baltimore. “Temperatures at or near boiling basically cook normal biological material and destroy proteins, lipids and genetic material.”
But high temperatures are not the only problem faced by organisms in the springs. Some pools are very acidic, close to pH2, whilst others are very alkaline and go up to pH10.5.
You can easily fall into the boiling clay or inhale poisonous fumes
The waters can be very salty, and many pools are rich in potassium, boric acid, silicic acid and sulphate. There is little oxygen in the pools, as at high temperatures less oxygen can dissolve in water.
Conditions are so challenging that no complex organisms can survive them. Animals generally struggle when they are exposed to temperatures much above 50C – true even of the Pink Pompeii worms that live next to deep-sea hydrothermal vents spewing out water at 400C onto the ocean floor.
Most living creatures that thrive in extremely hot environments are single-celled bacteria or archaea. These are the simplest life forms on Earth, and probably the oldest. They consist of just one cell and lack the more sophisticated cell machinery that more advanced organisms have.
Keen to learn more about the types of creatures found in the boiling pools, and making sure to keep a lookout for the occasional bear, the international team of scientists has collected samples and analysed the DNA they contain for clues to the microbes’ extreme resilience. When exploring the hydrothermal fields, the scientists wore thick rubber boots up to the thigh, just in case they accidentally broke through the crust to the boiling water below.
Many of them can grow using carbon monoxide, which is normally an extremely toxic gas
They found a whole host of microorganisms, including entirely new species never seen before.
Desulfurella acetivorans, for instance, is a bacterium that thrives in pools at 58C. It feeds on organic acetate in the pool. Rather than breathing oxygen, these microbes get their energy from volcanic sulphur through a process known as sulphur reduction.
Then there is Thermoproteus uzoniensis. This new species of archaea was found thriving in the hot springs, steam vents, mud holes and soils in the Uzon Caldera and Geyser Valley.
The rod-shaped microbes can survive in waters close to boiling point by feeding on the fermented remains of organic molecules called peptides. They also use sulphur reduction for energy. Scientists believe that strains of closely related T. uzoniensis are so common across the region because they are being carried between pools by wind, water, birds or even bears.
Acidilobus aceticus is so named because of the extreme acidity – pH2 – of the hot spring in which it was found. The acidic water was also very hot, at 92C. The microbe feeds on fermented starch and, again, uses sulphur to power its metabolism.
It is not just sulphur ‘breathing’ microbes that thrive in hot pools and geysers, though. Bacteria growing on other volcanic gases such as carbon dioxide, carbon monoxide, and iron and nitrates were also found.
The scientists wore thick rubber boots up to the thigh, just in case they accidentally broke through the crust to the boiling water below
“We found a great many different species of thermophilic [heat adapted] bacteria from Kamchatka,” says Robb. “An unusual feature of the system is that many of them can grow using carbon monoxide, which is normally an extremely toxic gas.”
The biggest and hottest pool in the Uzon Caldera is the Bourlyashchy Pool. The name is Russian for ‘bubbling’, and is so called because of the gases that are constantly being released from it.
At 97C it is the hottest thermal environment ever studied for signs of life on land. But in one of the most recent expeditions to the site, researchers found a large number of microbes living there.
Many of the bacteria found in the pool were of the order Aquificales, which have also been found in hot springs in Yellowstone National Park in the western US. The microorganisms get their energy from hydrogen in the pool.
Not all of the microbes in Kamchatka are new species. Some have been seen before, in hot springs in Yellowstone, Iceland and New Zealand. These tiny life forms have carved out a niche for themselves in Earth’s hottest and most inhospitable environs, but what allows them to do so?
The bacteria and archaea found in Kamchatka – and in other hot springs around the world – have unique adaptations that allow them to thrive at high temperatures.
The world record for surviving hot temperatures has been raised several times now
Normally the lipid membranes which encase living cells fall apart above 50C, as the ester bonds between the fats break down. Some hot spring microbes get around the problem by using special ether bonds instead of esters, which are sturdier and more robust.
That is just the start, though. Proteins and enzymes that power all the chemical reactions inside cells denature and unravel at high temperatures, as does DNA.
The microbes have found ways to deal with the problem. Special sequences of amino acids appear to reinforce the proteins and protect them, whilst charged particles called ions buried inside the proteins may also make them more stable.
Another weapon in the thermophilic bacteria’s arsenal is a special category of molecules called heat shock proteins. These act as molecular chaperones and prevent proteins that have unravelled from sticking together. They also actively refold proteins that have collapsed from the heat, allowing the proteins to start functioning again.
There is also evidence that proteins in thermophilic microbes are more densely packed and compact than normal, which protects them from unravelling. And there may be extra bonds between different parts of each protein’s intricate 3D structure, helping to make the molecule more stable.
The microbe thrives at 121C and there are claims that it can even survive for two hours at 130C
Together, these strategies allow some microbes to push against the boundaries we once thought were vital for life to survive. The world record for surviving hot temperatures has been raised several times now.
A few years ago it was held by Pyrolobus fumarii, a species of archaea found in a black smoker hydrothermal vent on the ocean floor in the middle of the Atlantic. P. fumarii can live perfectly happily in 113C waters.
Since then, another group of scientists has found a microbe from deep-sea vents that is able to survive at 122C. And there are hints that even this is not the ultimate limit for life.
A new microbe, for now called “Strain 121”, has since been discovered in a thermal vent deep in the Pacific Ocean. The microbe thrives at 121C and there are claims that it can even survive for two hours at 130C. However the finding is still contentious, as the strain has not been made publicly available to study.
“Thermophilic microorganisms have special mechanisms that allow their biopolymers (proteins and nucleic acids) to maintain their structure and functionality at high temperatures,” explains Bonch-Osmolovskaya. “Membranes of thermophiles are also different, those of bacteria contain more saturated fatty acids, while in archaea the stability of membranes is caused by the presence of special lipids called isoprenoid ethers.”
Hot springs offer tiny glimpses into what life was like on early prehistoric Earth
These special adaptations are fascinating to scientists like Bonch-Osmolovskaya. But they are not the only ones with a professional interest.
Enzymes taken from thermophiles can work at higher temperatures, which makes them very attractive commercial prospects in industries including petroleum, chemical, pulp and paper. Heat-resistant enzymes are also very useful additions to detergents.
Even the field of forensic science has benefitted from research on thermophiles. A lot of forensic work involving DNA is only made possible by a special process called the polymerase chain reaction that replicates DNA and amplifies its signal to detectable levels. The DNA-replicating enzyme responsible was isolated from a thermophile.
Perhaps more importantly, the microbes living in the hot springs, which can survive scalding hot, acidic waters that would kill most other living beings, may hold the key to understanding the origins and early evolution of life on Earth.
Hot springs offer tiny glimpses into what life was like on early prehistoric Earth, when the first life forms came into being. There was little sunlight, no photosynthesis and no plants; and that means there was next to no oxygen in the thin, primitive atmosphere.
In the absence of a fully-formed atmosphere, harsh UV light destroyed the DNA of living creatures, meaning that life could probably only exist in the depths of the oceans, or below ground, where it would have faced similar challenging chemical conditions to those now seen in Kamchatka.
The conditions in Kamchatka also closely mirror those seen on some alien worlds in our solar system. If microbes can survive in hot springs here on Earth, on a diet of chemical energy from volcanoes, perhaps they could exist on other planets too.
Of course, journeying to those extraterrestrial environments to test the idea would make a trip to the Uzon caldera seem simple in comparison.