illustration Drüm | INFOGRAPHICS Tiago CirilloThey survive under conditions that are unthinkable for any other beings living on earth. Their homes are hyper saline waters, torrid deserts, volcano craters and Antarctic icebergs. These are live beings that can only be seen under a microscope, yet they are gigantic in terms of what they reveal to astrobiologists such as Claudia Lage, a professor at the Federal University of Rio de Janeiro (UFRJ). “The genetic structure of microorganisms such as viruses, bacteria and archaea is so diversified that they could have been formed in totally different places in the Universe,” she says. This notion is based on panspermia, a hypothesis that proposes that life originates in multiple points in the Universe, and not necessarily and exclusively on Earth.
The superhero of this world is the Deinococcus radiodurans bacteria, which is resistant to high radiation doses. In simulations in particle accelerators, these bacteria proved to be able to resist journeys in outer space while traveling in fragments of dust (see Pesquisa FAPESP issue 176). Without the protection of a spaceship, the interplanetary environment is deadly for live beings: extremely high doses of ultraviolet radiation and X-rays plus pitiless bombarding by particles accelerated by solar explosions make it impossible for any form of life to exist.
Claudia and biologist Ivan Paulino Lima, also from UFRJ, in partnership with researchers from the University of São Paulo (USP), from Italy, and from the UK, have concluded a new study showing that the Deinococcus can survive – without any major damage – the particles given off by solar winds, of which protons are the most harmful. This resistance would allow these bacteria, riding on the dust that is disseminated throughout the Universe, to travel for millions of years through outer space. This is enough time to travel from Mars to Earth, as was explained in the conclusion of the study published in Astrobiology at the end of 2011. This conclusion is based on experiments conducted with particle accelerators in Italy and in the UK. The experiments simulated the typical conditions of interplanetary voyages, including proton rays, carbon and electron ions in a vacuum, that would be faced by microorganisms travelling on their own or in the dust particles released by comets or asteroids. The experiment showed that the weaker energies, a characteristic of ordinary solar winds, have no effect on the Deinococcus bacteria, even when the latter are unprotected. The solar explosions release stronger and more lethal energies, but, depending on how strong they are, all the bacteria have to do is to stick to the dust particles – even as solar explosions release increasingly stronger and deadlier energies – to protect themselves from the bombarding of the particles. “These energies do not occur frequently enough to destroy the bacteria,” adds Ivan Paulino Lima, who is currently in California attending a postgraduate program at Nasa (the United States’ National Space Agency).
Danger in outer space
One of the study’s main findings is that outer space particles do not pose a major obstacle to these microorganisms. Therefore, cosmic dust is essential to protect the bacteria from ultraviolet radiation and rather than from bombardment by protons, to which the Deinococcus proved to be resistant. “Stars are true stations of radiation,” says the researcher. The study showed that at the end of an interplanetary voyage, the superbacterium would have survived long enough to land on Earth, even though it had come close to the Sun. According to the research, it could resist for more than a year – 420 days – the doses of ultraviolet radiation commonly found on the Earth’s orbit, even without the protection of the atmosphere. The time limit was not defined by the athletic fitness of the potential extraterrestrial travelers, but by the available period that the researchers had to conduct tests at the National Synchrotron Light Laboratory (LNLS), the particle accelerator in Campinas, São Paulo State. It is possible that the bacteria could survive for much longer.
Another recent research project of the group, also published in Astrobiology, expanded on the possibilities of survival in outer space and showed that this bacterium is not the only live being able to survive under the harsh conditions of the regions near stars and planets, conditions even more lethal than the bombardments in the interplanetary zone. Two other microorganism species – the Natrialba magadii and the Haloferax volcanii – also survived high doses of ultraviolet radiation, although this radiation was weaker than that supported by the champion among the bacteria. “They resembled the Deinococcus in this respect,” says Claudia, “and this in itself is impressive, as they were subject to extremely high doses of radiation.” This is the first time that this kind of organism – archaea, forms of life that for a long time had been confused with bacteria, but are actually very different from the genetic and evolutionary point of view – is put through a simulation of interplanetary conditions. Of the two, the N. magadii was the most surprising, having proven to be even more resistant to the preparatory treatment for the experiments – which included high vacuum and dehydration – than even the Deinococcus. This preparatory treatment was powerful enough to exterminate non-extremophile bacteria such as Escherichia coli, extensively found in human environments. Up to a certain level of radiation, the three microorganisms exhibited a similar survival capacity. N. magadii did better above this level; H. volcanii did not resist, possibly because it had become more fragile as a result of the vacuum. However, this has not discouraged Claudia. “Even when a significant portion of a sample is sprayed with radiation, some archaea survive the high dose of ultraviolet rays, perhaps to an extent that might enable the species to colonize other planets,” says the astrobiologist from UFRJ. “In the next simulation, we will submit them to conditions that are more similar to the ones in their natural homes,” she adds. Claudia justifies the importance of the test by explaining that cosmic dust can be comprised of various elements, including salts such as silicates or carbonates, which can provide several different degrees of protection.
The performance of the archaea under these harsh conditions is not entirely unexpected. Indeed, many species known to be extremophiles, i.e., they thrive under harsh circumstances and populate different kinds of unpleasant environments, such as hyper saline waters and smoke-spouting volcanic craters. In Claudia’s opinion, the research study results are important because they illustrate the enormous difference between bacteria and archaea. “Archaea are a separate kingdom and are considered more primitive than bacteria.” Thus, the findings suggest that the simplest forms of life might be able to travel and to colonize different places on the Universe.
According to Claudia, the cell membrane is essential for this protection, to prevent radiation from affecting the genetic material. This membrane is similar in the three species studied by Claudia’s group. This was unexpected because it is not typical in bacteria such as the Deinococcus. In the case of the archaea, offsetting mechanisms in the membrane prevent water loss, even in hyper saline environments. The researchers believe that this protects the cells from radiation, even though the cell envelope of the N. magadii has not been studied in detail yet. The Deinococcus has another characteristic besides its reinforced membrane: each bacterium is comprised of four parts, as if it had begun to split, without this process being completed. As a result, the organism has additional copies of its full genome, enabling it to retrieve information if one of the parts is destroyed.
In their search for signs of distinct origins of life, the researchers are analyzing in detail environments in which only extremophile bacteria can survive, such as Lake Vostok, which lies deep in the Antarctic subsoil. The region was perforated by Russian scientists in February. One of the recent discoveries in extreme environments of this planet is a bacterium found in Antarctica, which is being studied by Amanda Bendia, one of Claudia’s students. Amanda is going to present her master’s thesis this month. When submitted to high doses of ultraviolet rays, these still nameless bacteria reacted like the Deinococcus. The next step is to discover the identity of these newly found bacteria. If it is another species of Deinococcus, it will prove to be the first member of a genus adapted to extremely high temperatures yet able to survive in ice. If it is a different bacterium, it will be one that is more independent and able to survive under outer space conditions. Both are exciting possibilities.
In addition to exploring the possible existence of live beings circulating around the Universe (even though they differ a lot from the Martians in space ships that we see in films), research studies in this field also have practical applications: namely, finding out what is needed to kill these super powerful bacteria. “Before sending a probe to Mars, it is necessary to develop extremely powerful sterilization processes so that these extremophiles do not leave the Earth,” Claudia explains.
This story will probably expand going forward, when AstroLab – the laboratory located in the city of Valinhos, State of São Paulo – goes into full operation. This lab is to specialize in investigating possibilities of life in outer space. One of the National Science and Technology Institutes (INCTs) funded by FAPESP and by the National Council of Scientific and Technological Development (CNPq), the center has, since January, been analyzing micro communities living in harsh environments, such as icebergs and the bottom of the sea. “The great advantage is that we can conduct all the steps – from the storage of samples to outer space simulations – at one facility,” says Douglas Galante, from the Institute of Astronomy, Geophysics and Atmosphere Sciences at the University of São Paulo (IAG-USP), and one of the coordinators of the new research center, together with Fabio Rodrigues and Rubens Duarte, both from USP. At present, the equipment that will allow outer space conditions to be simulated is stored on a ship on its way to Brazil. Galante promises to have good news very soon.
PAULINO-LIMA, I. G. et al. Survival of Deinococcus radiodurans against laboratory-simulated solar wind charged particles. Astrobiology. v. 11, n. 9, p. 875-82. nov. 2011.
ABREVAYA, X. C. et al. Comparative survival analysis of Deinococcus radiodurans and the haloarchaea Natrialba magadii and Haloferax volcanii, exposed to vacuum ultraviolet radiation. Astrobiology. v. 11, n. 10, p. 1.034-40. dec. 2011.