Hikoaki Yamagishi, a Japanese scientist researching radiodurans
If life can be found on Mars, which type is most likely? Some scientists once said that whether it is on Venus, Mars or distant Jupiter, do not expect to find intelligent creatures or other large creatures. On those planets, microorganisms represented by bacteria are most likely to thrive, because only microorganisms can cope with various extreme living environments freely. These seemingly tiny creatures that are indistinguishable to the naked eye are the most tenacious life forms in the universe.
Bacteria that are not afraid of space radiation
The International Space Station operates in space about 400 kilometers from the ground, where it is a typical space environment: cold, vacuum, and full of intense radiation. Some Japanese scientists have discovered that radiodurans can survive in this extreme environment.
Hikoaki Yamagishi of the University of Tokyo, Japan, and others once placed some colonies of radiococcus on the panel outside the International Space Station. After 3 years, the researchers found that all colonies larger than 0.5 mm in diameter survived. Further studies have shown that the bacteria in the outer layer of these colonies will form a protective layer after death, which can help the bacteria inside to survive. These colonies can live on the panel outside the International Space Station for 15 to 45 years. Without attachments, colonies with a diameter of more than 1 mm can survive freely floating in space for more than 8 years.
The reason why most organisms are afraid of radiation is that radiation can greatly damage DNA. Previous scientific studies have shown that the tenacious vitality of radiodurans lies in its super-strong DNA self-healing ability. Yamagishi said that if microorganisms are discovered on extraterrestrial planets in the future, they may not be natives, but creatures that have been sown on other planets by human spacecraft. Of course, this can also prove that the ancestors of life on earth may also originate from meteors.
Bacteria that are not afraid of heat
General organisms are difficult to survive in an environment above 50°C, but thermophilic bacteria prefer relatively high temperature environments, and the optimum growth temperature is 65°C to 70°C. In the sulfur-containing hot springs of Yellowstone National Park in the United States, scientists once isolated a thermophilic facultative autotrophic bacteria-Sulfolobus sourthermum, which can grow at temperatures higher than 90°C.
Hot springs are not only on the ground, but also in the deep sea. Although the deep sea water is icy and bitter, the temperature of the hot spring on the seabed can exceed 100°C due to the high pressure on the seabed. In such deep-sea hot springs, there are also some thermophilic bacteria that live on sulfide. They are the lowest-end organisms in the food chain of the hot spring biota. In 1979, scientists discovered a powerful bacterium-Thermonet bacteria deep sea on the nutrient-rich edge of deep sea hot springs. In addition to being able to withstand the atmospheric pressure sufficient to press the submarine into pancakes, it also withstood the test of high temperatures exceeding 100°C.
At present, scientists have isolated some thermophilic bacteria for industrial production. For example, in the fermentation industry, production efficiency is often higher at high temperatures, while ordinary yeasts are difficult to survive at high temperatures. In addition, the participation of thermophilic bacteria in industrial production can ensure that the product will not be contaminated by other bacteria and viruses during the production process.
Bacteria that are not afraid of acid
Acidophilus is a kind of bacteria that is not afraid of acid. It is distributed in acidic mineral water and acidic hot springs. It usually lives in an acidic environment with a pH of 0.5 to 4. Some species can even live in an extremely acidic environment with a pH of less than 1. in. For example, Thiococcus acidophilus can live in an environment with a pH of 2.5 and a temperature of 70°C, which makes us have to admire the tenacity of life.
The acidic environment in nature usually contains a large amount of metal ions. In the smelting pond of a California mine in the United States, the iron ion concentration per liter of smelting pond water was as high as 111 grams, and other metals such as copper, arsenic, calcium, and magnesium also reached a few grams to tens of grams. For most organisms, high concentrations of heavy metal ions are harmful, but acidophilus bacteria can grow well and draw nutrients from it.
Acidophilus bacteria can live in solutions containing metal ions because they have a special ability to deal with metals: some can excrete metal ions inhaled into the body, some can store them in a specific place in the body, and Some can even convert metal ions directly into metals. Scientists at McMaster University in Canada have discovered that Delft acid bacteria can convert gold ions that are toxic to them into harmless gold nanoparticles. When those Delft acid-feeding bacteria sense the presence of gold ions in the environment, they release defibrillin A, a protein that converts gold ions into pure gold particles. Scientists are studying this bacteria, hoping to use it to extract gold from gold mine wastewater.
In many science fiction films, microorganisms such as bacteria and viruses from aliens have been demonized. The typical representative is the “Resident Evil” series of science fiction films. In fact, judging from the existing research results, those extraterrestrial microbes have a greater dependence on extreme environments, and it is difficult for them to spread wantonly in human living territories. Of course, the unknown is the most terrifying. Only when we know more about those special bacteria, can we effectively eliminate the fear of them and even turn them into beneficial friends for the benefit of mankind.