Bacteria-astronauts: together to distant planets

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Bacteria-astronauts: together to distant planets
Bacteria-astronauts: together to distant planets
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Man will soon go to Mars, and then, perhaps, to more distant planets. For this we design rockets and spaceships. We calculate favorable flight paths and send automatic probes in search of convenient places for landing and building bases. But so far this is not enough to go to the Red Planet tomorrow.

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We are all following high-profile Martian projects. But, as a rule, we lose sight of the work of scientists, the results of which will help to solve many problems necessary for long-distance space flights. This is now not about those scientists who design spacecraft. And about those who work with microorganisms, which should go to Mars and further along with humans.

Go not as unwanted fellow travelers or model organisms for experiments, but with more important roles.

Whose home is the ISS?

Microorganisms rush to colonize everything around on Earth, regardless of the severity of the conditions. They know how to adapt. Orbital stations have long been colonized by them. Crews come and go, but microbial colonies remain. They live and evolve. Of course, the International Space Station remains under human control, but for their invisible inhabitants, the ISS, and the Mir station earlier, have become a real home.

The first microorganisms went into space for the first time on August 19, 1960, on the Sputnik-5 spacecraft, the prototype of the Vostok spacecraft, on which Yuri Gagarin would later go into space. This flight lasted 25 hours, and the next day the descent vehicle successfully returned the entire "crew" to the ground. On this day, living beings for the first time returned to Earth from orbital flight.

True, then few people remembered about nameless microbes, the main characters of the flight were the dogs Belka and Strelka. Several species of microbes (Escherichia coli, Staphylococcus and Enterobacter aerogenes) were just one item on a long list of living things and biological objects sent from Earth into space. Among them were also mice, insects, fungal crops, plants and seeds.

Many types of microorganisms have been in orbit since then. They can be conditionally divided into two groups: those that are transmitted from person to person and extremophiles. The study of the former is important for the well-being of people on Earth and in future space missions, and of the latter, for understanding the physiological threshold for survival in outer space.

Space agencies have been monitoring the microbial environment of the ISS for many years. In 2021, geneticists from the University of Southern California (USA) and the University of Hyderabad (India) identified microorganisms that were found in samples taken on the ISS back in 2015-2016. Of the four bacterial strains, only one was previously known - Methylorubrum rhodesianum, the remaining three were classified as new species. Although they all belong to the same family.

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Terrestrial relatives of bacteria-astronauts live in soil and fresh water. These bacteria are involved in the process of nitrogen fixation, which means they play an important role in the growth and development of plants. On board the station, they were most likely in connection with experiments on growing plants. The ISS grows various types of vegetables, such as tomatoes and lettuce. Scientists believe that the microorganisms found may be useful for future missions to other planets. The crew will have to grow their own food on such flights, you can't take everything from Earth.

The astronauts have already collected about a thousand samples at the station.All of them are awaiting to be sent to Earth, so new discoveries await scientists ahead.

Not all microorganisms enter space purposefully during experiments. Some come with people as part of the microflora, others with equipment that cannot always be thoroughly cleaned before starting. Once in new conditions, the microorganism either dies or adapts. Only the most persistent survive. They change their eating habits and learn to live in a new environment for themselves. Once mastered, they can harm equipment or even cause illness in the crew. Therefore, as experts warn, in the conditions of a long space flight, operational microbiological control is necessary.

For this case, the Energia rocket and space corporation has developed the E-Nose scientific device, or, more simply, the "electronic nose" which should sense unwanted fellow travelers. The device is capable of capturing volatile metabolic products of microorganisms and allows you to determine the quantitative level of bacteria and microscopic fungi on surfaces without sending samples to Earth. In 2012, the "electronic nose" was in orbit, and allowed to detect both fungal and bacterial contamination of some surfaces of the ISS.

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It is now clear wherever we go, the microbes will fly with us. And better as helpers than uninvited guests.

Irreplaceable companions

We understand that it is cheaper to explore and conquer space using robots. It is easier to launch an automatic station to a distant planet than to send a person there. The machine does not ask for food or drink, it does not need protection from radiation, such as a person needs. It consumes much less energy.

To send a man to Mars, he needs to build a whole house in space, "fill" it with water, food, oxygen, take care of waste collection and recycling, and figure out what to do on a long flight. In order to lift everything into orbit and send it to Mars, you need powerful rockets, a lot of fuel and a lot of time.

Scientists at Lawrence Berkeley National Laboratory in the United States have proposed lowering the cost of an expedition to Mars by using synthetic bacteria to produce fuel, food, and drugs for long missions, and have calculated the benefits of this approach to the task.

So, for a flight lasting 916 days, you need to take about 10 tons of food with you. But this amount can be significantly reduced if photosynthetic bacteria are used in the expedition. During the flight, the raw material will be the waste of the astronauts, and, upon arrival on Mars, also the decay products of the Martian atmosphere and soil, where carbon dioxide and nitrogen are abundant.

The mass of fuel required for the round trip should be two-thirds of the mass of the expedition ship. But after all, everything necessary for the production of fuel but the way back can be taken in the Martian atmosphere, from which bacteria can synthesize methane.

In total, the mass of fuel can be reduced by 56 percent, food supplies by 38 percent, and building materials, to create a base on the planet, by 85 percent. The use of synthetic biology will significantly reduce the cost of sending spacecraft to Mars, which means they will make such a flight more realistic and close, according to Berkeley.

Scientists from the Institute of Problems of Chemical Physics of the Russian Academy of Sciences (IPCP RAS) are working on an apparatus that will allow the disposal of organic waste in space flight. A colony of microorganisms will be placed inside it. The bacteria will not only recycle waste but also generate electricity.

Now the specialists of the institute are busy with the selection of the optimal composition of the colony of microorganisms that could live in symbiosis with their small ecosystem. This work is being carried out jointly with the State Research Institute of Genetics and Selection of Industrial Microorganisms Federal State Unitary Enterprise.Previously, they were already engaged in the development of biofuel cells based on the bacteria of the genus Shewanella. It is supposed to experiment with both existing organisms and create genetically modified bacteria with desired properties.

From food to medicine

As we can see, we can say that scientists are already "selecting" the crew for the flight. Some of the candidates have already been in space. True, not entirely successful. In 2019, the German Aerospace Center (DLR) planned to conduct an interesting experiment Eu: CROPIS (Euglena and Combined Regenerative Organic-food Production in Space) in orbit. The name is translated as "Euglena and the combined regenerative production of organic food in space." The purpose of the experiment was to study the possibility of growing food in space at future lunar and Martian stations.

Its place was not the ISS: a special spacecraft was created for the experiment - a small mini-satellite, which is a greenhouse, or rather two greenhouses. The first was supposed to simulate lunar gravity during the first six months, the second Martian during the next six months. The level of gravity corresponding to the Moon and Mars was modeled by rotating the cylindrical body of the spacecraft around its longitudinal axis.

It was planned to grow tomatoes using synthetic, since this is still an experiment, urine. Urine recycling is a problem in space flight. However, in the future it is planned to use it for growing fruits and vegetables, turning it into easily digestible fertilizers. The unicellular alga Euglena Gracilis should help in this. The colony of these microorganisms was supposed to protect the biosystem created on the satellite from high concentrations of ammonia, and the oxygen produced by the algae was needed to convert urine into nitrates until the tomatoes themselves produce a sufficient amount of photosynthetic oxygen.

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However, the main experiment with Euglena failed due to a software problem. Perhaps it will be repeated. But the auxiliary Anabaena with cyanobacteria was successful. The Ames Research Center (USA) changed the genes of this bacterium in such a way that it feeds other genetically modified bacteria with sugars, which, in turn, should become raw materials for food, fuel and medicines.

To track how successful the experiment was, since it was not supposed to return the device to Earth with the results, a functional companion, the bacterium Bacillus subtilis, went along with the bacterium. Her task is to be an indicator in this experiment, she is able to convert sucrose obtained from Anabaena into a red pigment. A special sensor was supposed to record color changes, and transmit data to Earth, which would act as proof that the bacterium functions well in space. The experiment is reported to have been successful and generated a large amount of data.

In fact, many researchers are pinning their hopes on cyanobacteria. Let us recall that oxygen in the atmosphere of our planet appeared due to their activity.

Researchers at the University of Bremen have created a bioreactor that should be an indispensable aid for Martian colonists. It produces oxygen and nutrients from raw materials that can be found on Mars, and inside it, already known to us, Anabaena.

In a bioreactor called Atmos (an atmosphere of "Martian" gases is created in it), the cyanobacteria of the Anabaena sp. PCC 7938 has a long list of merits. On the one hand, these bacteria are able to withstand the harsh conditions of space travel, on the other, Anabaena can assimilate gaseous nitrogen and convert it into forms available to other organisms, that is, enter it into the food chain.

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To make it clear, Anabaena are close relatives of the cyanobacterium of the genus Arthrospira, which have been consumed by humans since ancient times. Members of the genus Arthrospira are cultivated all over the world.They are used as a food additive and as a stand-alone product. Sold in the form of tablets, flakes and powder, as well as a feed additive for fish and poultry farming. And Arthrospira is known under the commercial name "Spirulina". Scientists suggest using this method and cyanobacteria of the genus Anabaena, slightly correcting their genome.

Experiments have confirmed that the Anabaena sp. PCC 7938 reproduces well in a bioreactor, which means it can serve as a source of organic matter and oxygen for future colonists of the Red Planet.

The researchers also demonstrated that the resulting biomass can be used to grow Escherichia coli bacteria, a favorite subject of genetic engineers. These genetically modified bacteria can be used to produce many substances and drugs needed by the Martian colonists, in particular.

However, we still need to fly to Mars without getting sick, so the medicines can be useful to us on the ship. We can calculate how much food we will need for an expedition to Mars, but how much medicine we will need is harder to say. We cannot imagine how often astronauts will get sick, and most importantly with what. What if, during the flight, astronauts encounter previously unknown diseases or known ones manifest themselves from a new, previously unknown side.

In addition, according to Clay Wang, professor of pharmacology at the University of Southern California, many drugs deteriorate faster in space than on Earth. If you go on a long space flight, you will have to grow medicines on the way on the ship.

The university's laboratory is working to turn the fungus Aspergillus nidulans, and possibly other fungi, into factories capable of producing the medicines astronauts need. "Genetic analysis shows that this fungus can produce about 40 beneficial molecules, including a drug for osteoporosis, one of the main threats to astronauts' health," says Wang.

In 2016, as part of his research, Wang, together with NASA, sent several different strains of the fungus Aspergillus nidulans to the ISS. The study included one so-called wild-type strain and three mutant strains, two of which were genetically modified to increase the production of secondary metabolites.

The high level of background radiation and life in an almost complete absence of gravity should have created a stressful situation for the bacteria and forced Aspergillus nidulans to produce those molecules that this fungus is not able to create in more favorable conditions on Earth. The results of an experiment by Wang's team, published in 2019, showed that being at the station did indeed alter the genome of the fungus in some areas of DNA, alter the process of protein production, and affect metabolism. But, it is still far from practical results.

Genetic engineering can turn mushrooms into versatile drug factories. Antibacterial, antifungal and anticancer drugs can be produced on board spacecraft. It is enough just to take on a flight several spores of each strain, and, if necessary, grow them with the necessary medicine "on demand".

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Perhaps, the necessary strain in the "first-aid kit" of the astronauts will not be found. But even in this case, the sick astronaut will not be left without medicine. In this case, there will be a DNA printer on board. The recording of the desired gene sequence will be sent from Earth by radio, and the cell grown from synthetic DNA will produce the necessary medicine.

Mars is waiting. Not only us

In primitive times, a person, settling around the planet, took with him animals already domesticated by that moment. Thanks to them, people had food, clothing, transportation, protection, and it was easier for them to settle in a new place.

The colonial ship of the future is unlikely to resemble Noah's ark. Going to Mars, for obvious reasons, we will not take pets with us.But genetically modified bacteria will definitely fly with us, and possibly even before us. They will help us settle in a new place. And the first thing that "domesticated" bacteria will help us with is the construction of a Martian settlement. Building on Mars will require a lot of materials. From home, you can only take something light with you - for example, inflatable modules or too technological, which you definitely cannot create on an alien planet. But we need a foundation for solid structures.

Researchers from the University of Colorado (USA) made bacteria turn sand into bricks. Moreover, the material turned out to be as durable as ordinary concrete. The production of such a biobrick is based on bacteria of the genus Synechococcus. They were placed in a hydrogel nutrient medium and mixed with sand. Bacteria, fed from this environment, grow and produce calcium carbonate. That is, the process of mineralization starts - similar to the formation of a shell in mussels.

"Such material will certainly come in handy in conditions with limited supplies of raw materials, for example, in the desert or on the Moon or Mars," says Will Srubar, co-author of the study. “In a barren environment, these building materials are very good, in that they mostly require only the Sun to grow. I think one day we will not take bags of cement with us to Mars, but bioorganisms,”he adds.

Scientists from Brown and Stanford Universities (USA) want to use the soil bacterium Sporosarcina pasteurii for the production of building materials on Mars. She uses urea (which is also in urine) to produce ammonium. At the same time, the environment surrounding the bacterium becomes alkaline, which allows the formation of a natural cement slurry based on calcium carbonate. From it, you can get both the brick itself, mixing with the red dust of the planet, and masonry mortar for connecting the bricks obtained.

To believe their assumptions, scientists performed an experiment. They took bricks from rocks most similar to Martian ones, settled bacteria between them and provided them with urea. After two weeks, the bricks were firmly bonded with the resulting biocement.

But not everything can be built from concrete, what about metal structures? This is where biomining comes to the rescue. It is such a potentially cheaper alternative to traditional mining, where the required materials from the rock are extracted with the help of bacteria.

Microorganisms play an important role in the weathering of rocks on Earth: they can oxidize or reduce the chemical elements that make up minerals, and also accelerate corrosion. These properties of bacteria have learned to use for mining (biomining), and cleaning contaminated soils (bioremediation). This method has already been tried on Earth, why not try it in space.

According to Benjamin Lehrer from the Delft Technical University, before sending people to Mars, special unmanned systems must be sent to the planet, including: a rover, a bioreactor and a 3D printer.

The rover will be collecting iron-rich Martian regolith, delivering it to the bioreactor and loading it. There it will be treated with Shewanella oneidensis bacteria. These bacteria are capable of converting Martian regolith into magnetite, a magnetic iron oxide, which can then be extracted using magnets. After that, in a 3D printer, magnetite will be turned into ordinary metal elements necessary for construction: screws, nuts, iron sheets, etc. One such "metallurgical complex" with a bioreactor volume of 1400 liters will be able to produce up to 350 kg of metal products per year.

Several such unmanned modules, sent in advance to Mars, will be able to print all the necessary structures and elements to create a habitat on the planet. People who arrived later will only have to put everything together.

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But will biomining work outside of Earth? In 2019, scientists from the University of Edinburgh, as part of the ESA BioRock project, decided to find out and conducted an experiment in orbit. There was some doubt that bacteria would be able to mine metals just as efficiently in reduced gravity as they would on Earth.

Samples of rocks, strains of bacteria, as well as special bioreactors equipped with centrifuges for simulating gravity were delivered to the ISS. Basalt was chosen as the rock. It is relatively rich in rare earth metals and is common on the Moon and Mars as well.

In total, three species of bacteria were tested - Bacillus subtilis, Cupriavidus metallidurans and Sphingomonas desiccabilis. They were placed in a specially designed KUBIK bioreactor, in which, thanks to a centrifuge that spins the medium at the right speed, it is possible to simulate gravity levels similar to conditions on the Moon, Mars or Earth. Or, do not turn on the centrifuge, which will correspond to the conditions for the extraction of metals on asteroids.

The winner in this test and a candidate for future flights to the celestial bodies of the solar system was the bacterium Sphingomonas desiccabilis. It has demonstrated good bio-production results under all gravity conditions.

Scientists, as we can see, have been looking for useful microorganisms for a long time to accompany humans on long-distance space flights. Some are engaged in theoretical developments, others are conducting experiments on Earth, and someone is already sending microbes into space. Who exactly will fly, geneticists and biologists will answer, and we'll see. But it is already clear: we will not fly without them. It seems that it is in these invisible creatures that the solution of many problems associated with flights to distant planets is found.

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