Fungal attack in the NASA clean room

Mushrooms in the meteorite laboratory could spoil the detection of extraterrestrial molecules

Moon rock samples in a NASA clean room. The detection of fungi in another NASA clean room could mean that these samples are also contaminated. © NASA / James Blair and Lauren Harnett
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Earthly contamination: In a supposedly sterile NASA meteorite laboratory in Houston, researchers have detected an unexpected number of fungal spores - just in time. Because in this and other NASA clean rooms in future samples from Mars and the asteroid Bennu should be stored and examined. Contamination with terrestrial mold could distort analyzes of these space objects - and perhaps has already done so with meteorites and lunar rocks.

Sterile clean rooms are doubly important for space missions. On the one hand, they should prevent terrestrial microbes from being brought to other celestial bodies by space probes and landing modules, thus contaminating the extraterrestrial environment. On the other hand, they should ensure that samples from space or from the Moon, Mars and asteroids can be stored and analyzed under sterile conditions.

How pure are the NASA cleanrooms?

However, keeping these space cleanrooms sterile is obviously harder than expected. As early as 2013, researchers in the clean rooms of the NASA Jet Propulsion Laboratory (JPL) and the Kennedy Space Center, but also at the ESA in Kourou, discovered stubborn bacteria that apparently survived in the hostile environment of such clean rooms.

Now Aaron Regberg of NASA's Johnson Space Center (JSC) and his colleagues have discovered another contamination. Affected is the meteorite laboratory at the JSC, a clean room where meteorites previously found in Antarctica have been stored and analyzed. The researchers had taken swab samples from the floor, tables and a special work area for processing meteorite samples and cultivated them on nutrient media.

Penicillium mold under the microscope © Jon Houseman and Matthew Ford / CC-by-sa 3.0

Mushroom spores everywhere

The result: the samples were contaminated. "We found between four and 28 colony-forming units per 25 square centimeters, " report Regberg and his colleagues. The surprising, however: unlike earlier finds, it was not bacteria, but primarily mold fungi: they accounted for 83 to 97 percent of the proven contamination. display

This is questionable for two reasons, as Regberg explains. He and his colleagues cultivated the samples during their tests in such a way that both bacteria and fungi grow and can thus be detected. However, this has not happened in the previous tests of most other NASA premises. Therefore, according to the researchers, it can not be ruled out that the other cleanrooms also have hitherto unrecognized contamination with fungi.

Amino acid from the mushroom instead of from space?

Another problem: infestation with mold fungi can chemically change rock samples and thus spoil the analyzes. In addition, some molds produce exotic amino acids such as α-aminoisobutyric acid or isovalin. "These amino acids are usually considered extraterrestrial in origin, if detected in meteorites, " says Regberg.

The discovery of fungi in the meteorite clean room now questions this assumption. "Most of the mushrooms we have identified belong to the genus Penicillium and at least one species of this genus can produce α-aminoisobutyric acid, " the researchers report.

For the first time, the NASA space probe OSIRIS-REx is to return samples from an asteroid to Earth. NASA

Indeed, a few years ago NASA researchers discovered that supposedly alien amino acids in the lunar rocks of the Apollo missions are largely of earthly origin. The α-aminoisobutyric acid also found in these samples, however, still classified them as likely from meteorites at that time. The possible fungal contamination of the clean rooms now raises doubts.

Future rehearsals endangered?

The new finds are also explosive, because in the near future several space missions will take samples of asteroids and from Mars and bring them back to Earth. One of these missions is the OSIRIS-Rex spacecraft, which will arrive at the asteroid Bennu in the fall of 2018 and is expected to salvage samples from its surface. The first rock samples from Mars, on the other hand, are to return the NASA mission "Mars 2020".

In order to prevent contamination of these valuable samples, all of the planned clean rooms must now be re-examined. Regberg and his colleagues also want to use DNA analysis to determine the exact species composition of the mushroom finds. "It is very important now to pinpoint and minimize the microbiology of the future storage locations of these samples, " the researchers emphasize. (49th Lunar and Planetary Science Conference 2018)

(NASA, 27.03.2018 - NPO)