Throughout the history of our planet, people have coexisted with bacteria and viruses. We were looking for ways to resist bubonic plague and smallpox, and they in return sought ways to infect us. Already for almost a hundred years we have been using antibiotics, since Alexander Fleming discovered penicillin. In response, the bacteria acquired resistance to antibiotics. The battle has no end. We spend so much time with pathogens that in turn we start each other to a dead end. But what happens if we suddenly encounter deadly bacteria and viruses that have not been seen for thousands of years or have never been seen?
Perhaps we will soon find out. Climate changes are caused by the melting of permafrost soils that have been frozen for thousands of years, and as the soils are melting, ancient viruses and bacteria come to life and return to life.
In August 2016, in a remote corner of the Siberian tundra, on the Yamal peninsula, a 12-year-old boy died and at least twenty people were hospitalized after anthrax infection.
It was suggested that more than 75 years ago a deer infected with anthrax died and its frozen skeleton was trapped under a layer of frozen soil, under permafrost. There he stayed until the summer of 2016, when due to severe heat, the permafrost thawed. Thus, she released a deer dead body and anthrax infection in the nearest waters and soils, and then into the food reserve. People were threatened.
It’s scary that this may not be a single case.
The earth heats up and thaws more than permafrost. Under normal conditions, the surface layers of permafrost depth of about 50 centimeters melt each summer. But global warming gradually reveals the old layers of permafrost.
Frozen perennial soil is an ideal place for bacteria to remain alive for long periods of time, perhaps millions of years. This means that melting ice can potentially open a Pandora’s box with diseases.
The temperature in the polar circle grows rapidly, about three times faster than in the rest of the world. Other infectious agents can go outside.
“Permafrost is an excellent keeper of microbes and viruses because it is cold, dark and there is no oxygen in it,” says the evolutionary biologist Jean-Michel Claverie of the University of Aix-Marseille in France. “Pathogenic viruses that can infect animals and plants could be stored in old, frozen layers of soil, including those that caused global epidemics in the past.”
Only in the early 20th century more than a million reindeer died of anthrax. In the north, it is not so easy to dig deep graves, so most of these carcasses were buried close to the surface, in 7000 scattered burials in the north of Russia.
What else can hide under the frozen soil?
People and animals were buried in the permafrost for hundreds of years, so it is possible that other infectious agents can go outside. For example, scientists have discovered fragments of RNA of the Spanish influenza virus in corpses massacred in the Alaska tundra. Smallpox and bubonic plague are also buried in Siberia. In a 2011 study, Boris Revich and Marina Podolnaya wrote: “As a result of permafrost thawing, the vectors of fatal infections of the 18th and 19th centuries may return, especially near the cemeteries where the victims of these infections were buried.”
In the 1890s, a serious epidemic of smallpox occurred in Siberia. One city lost up to 40% of its population. The bodies were buried under the upper layer of permafrost on the bank of the Kolyma River. After 120 years, the Kolyma floods began to destroy the banks, and the melting of permafrost accelerated this process of erosion.
In a project that began in the 1990s, scientists from the State Research Center for Virology and Biotechnology in Novosibirsk studied the remnants of Stone Age people found in southern Siberia, in the Gorny Altai region. They also studied samples from the corpses of people who died during the viral epidemics in the 19th century and were buried in the permafrost of Russia.
Scientists say that they found bodies with ulcers, characteristic of smallpox traces. Although they did not detect the smallpox virus itself, they found DNA fragments.
Of course, this is not the first time that bacteria frozen in ice again come alive.
In a 2005 study, NASA scientists successfully resurfaced bacteria in a frozen pond in Alaska for 32,000 years. The microbes called Carnobacterium pleistocenum have been frozen since the Pleistocene, when the woolen mammoths were still wandering around the Earth. As soon as the ice melted, they again began to swim as if nothing had happened.
Two years later, scientists managed to revive a bacterium 8 million years old, which slept in the ice under the surface of the glacier in the valleys of Beacon and Mullins in Antarctica. In the same study, the bacteria were recovered from ice, which was over 100,000 years old.
However, not all bacteria can return to life after freezing in permafrost. Anthrax bacteria can do this because they form extremely hardy spores that can live in the frozen state for a very long time.
Other bacteria that can form spores, and therefore survive in permafrost, include tetanus and Clostridium botulinum, responsible for botulism: a rare disease that can cause paralysis and lead to death. Some mushrooms can also survive in permafrost for a long time.
Some viruses can also survive for long periods of time.
In a study in 2014, scientists led by Clavery revived two viruses captured by the permafrost of Siberia for 30,000 years. Known as Pithovirus sibericum and Mollivirus sibericum, they are considered “giant viruses” because, unlike most viruses, they are so large that they can be seen under an ordinary microscope. They were found at a depth of 30 meters in the coastal tundra.
Immediately after the revival, the viruses became contagious. Fortunately for us, these viruses infect only single-celled amoebas. Nevertheless, the study suggests that other viruses that can infect humans can also be regenerated.
Moreover, global warming need not necessarily melt permafrost to pose a threat. As the Arctic sea ice melts, the northern shore of Siberia becomes easier to reach by sea. Obviously, its commercial development becomes more profitable, including the extraction of gold and minerals, the drilling of oil wells, and the extraction of natural gas.
“At the moment, these areas are empty, and no one touches the deep layers of permafrost,” says Claveri. “But these ancient layers can be obtained in the process of excavation and drilling operations. If viable virions there still live, it will be a disaster. ”
Giant viruses can become the most likely culprits of a viral outbreak.
“Most viruses are rapidly inactivated outside host cells because of light, drying, or spontaneous biochemical degradation,” says Claveri. “For example, if their DNA is damaged and can not be restored, the viruses stop being contagious. However, among the known viruses, giant viruses, as a rule, are very strong and resistant. ”
Claveri says that viruses can emerge from the very first people who inhabited the Arctic. We could even see the viruses of long-extinct species of hominids like Neanderthals and Denisians who settled in Siberia and were exposed to various viral diseases. In Russia, the remains of Neanderthals aged 30-40 000 years were found. Populations of people lived there, ached and died thousands of years.
“The possibility that we can get infected with a virus from a long-disappeared Neanderthal man suggests that the idea that a virus can be” eradicated “from the planet is wrong and gives us a false sense of security. That’s why the stocks of the vaccine should be kept just in case. ”
Since 2014, Claveri has been analyzing the DNA content in permafrost in search of a genetic signature of viruses and bacteria that can infect humans. He found a lot of bacteria that can be dangerous to people. Bacteria have DNA that codes for virulence factors: molecules that produce pathogenic bacteria and viruses that increase their ability to infect the host.
Claverie’s team also discovered several DNA sequences that seem to have taken on viruses that included herpes. But traces of smallpox have not yet been found. For obvious reasons, they did not attempt to revive any of the pathogens.
It may well be that pathogens, from which people have already lost their habit, can manifest themselves in other places, not just from ice or permafrost.
In February 2017, NASA scientists said they found microbes 10-50,000 years old in crystals in a Mexican mine. These bacteria were located in the Cave of Crystals, part of the mine in Najce in northern Mexico. The cave contains many milky-white crystals of mineral selenite, which has formed over hundreds of thousands of years.
Bacteria were locked in small, liquid pockets of crystals, but as soon as they were pulled out, they were reborn and began to multiply. These microbes are genetically unique and may well be new species, but scientists have not yet published their work.
In the cave Lechugilia in New Mexico, 300 meters below the ground, found even more old bacteria. These microbes have not seen the surface for more than 4 million years. The cave has never seen sunlight and has been isolated for 10,000 years from surface water.
Despite this, the bacteria somehow proved resistant to 18 types of antibiotics, including drugs, which were considered the “last barrier” in the fight against infections. In a study published in December 2016, scientists found that bacteria known as Paenibacillus sp. LC231, were resistant to 70% antibiotics.
Because the bacteria were completely isolated in the cave for four million years, they did not come into contact with people or antibiotics that we treat infections. It turns out that their resistance to antibiotics appeared somehow differently.
Scientists believe that bacteria that do not harm people, among many others, develop a natural resistance to antibiotics. That is, this very resistance to antibiotics exists for millions or even billions of years.
Obviously, such antibiotic resistance could not develop in the clinic during the use of antibiotics.
The reason for this is that many types of fungi and even other bacteria naturally produce antibiotics in order to gain a competitive advantage over other microbes. This is how Fleming first discovered penicillin: the bacteria in the Petri dish died after contamination producing antibiotics by mold fungi.
In caves where there is little food, organisms must be ruthless if they want to survive. Bacteria like Paenibacillus might have developed resistance to antibiotics to avoid death from competing organisms.
This explains why bacteria are resistant only to natural antibiotics that come from bacteria and fungi, and make up about 99.9% of all antibiotics we use. Bacteria have never encountered artificial antibiotics, so they have no resistance to them.
“Our work and other people’s work suggests that resistance to antibiotics is not something new,” says microbiologist Hazel Barton of the University of Akron, Ohio, who led the study. “Our organisms have been isolated from surface species for 4-7 million years, but the resistance they have is genetically identical to that found in surface species. This means that these genes are at least the same old and appeared not because people started using antibiotic treatment. ”
Although Paenibacillis is not harmful to humans, in theory it can transmit its antibiotic resistance to other pathogens. But since it is isolated under 400 meters of rocks, this seems unlikely.
Nevertheless, the natural antibiotic resistance to antibiotics is probably so prevalent that many of the bacteria emerging from melting permafrost may already possess it. In support of this, in a 2011 study, scientists extracted DNA from bacteria found in permafrost 30 000 years old in the Bering Sea. They found genes that code for resistance to beta-lactam, tetracycline, and glycopeptide antibiotics.
Is it worth worrying about?
There is an opinion that the risk of the emergence of pathogens from permafrost is inherently incomprehensible, and therefore it is not worth worrying about. Instead, we must focus on the more obvious threats of climate change. For example, as the Earth warms up, northern countries may become more susceptible to outbreaks of “southern” diseases such as malaria, cholera and dengue fever, as their pathogens thrive in warmth.
Still there is an opinion that we should not ignore the risks when we can not quantify them.
“There is a non-zero probability that pathogenic microbes can reborn and infect us,” says Claveri. “It is not yet known how likely this is, but probably. Probably, these bacteria can be cured with antibiotics, resistant bacteria, virus. If the pathogen has not been in contact with people for a long time, the immune system will not be ready. So there is danger. “