gh COSMIC VERMIN

Inhabitants of old wooden and brick homes are well familiar with such a problem as fungi on the walls. However, it has turned out that cosmonauts at the International Space Station are also forced to endure this unpleasant neighborhood. A group of the Moscow researchers has studied specific composition of cosmic vermin microorganisms and simulated further colonies evolution and the harm they are able to cause to the ISS.

A space station is the increased risk zone with extreme conditions both for the people staying there and for equipment operation. Due to this, permanent control of all internal environment parameters, including microflora of the station, is a necessary condition of its reliable and secure operation.

Researchers from the Lomonosov Moscow State University and the A.N. Bach Institute of Biochemistry, jointly with specialists of the “ENERGIA (ENERGY)” Rocket-and-Space Corporation have for several years carried out monitoring of specific composition of microflora in the most contaminated areas of the ISS. And then, in terrestrial laboratories, they studied biocorrosion properties of educed microorganisms with the help of modeling experiments.

The issue of these “unpleasant cosmic neighbors” is not new – earlier investigations proved that long space flights of people on board orbiting stations discover a wide range of very different microorganisms, which get there with cargos delivered from the Earth and during the crew rotation. For example, back on board the MIR station, more than 200 bacteria and fungi species were discovered, among them being both conditional-pathogenous species and technophiles – a special group of microorganisms, which inhabit and destroy various industrial materials, including plastic and even metals.

Experiments on monitoring microorganisms that inhabit the station were also continued on the ISS. Cosmonauts take samples twice a year in the areas of possible accumulation and development of microorganisms, at that more than a half of these areas – different spots of the pressure body – the most crucial element of the station structure. Then the obtained samples are sent to the Earth, where specialists of the Faculty of Biology (Lomonosov Moscow State University) carry out their further investigation.

Seven completed investigation cycles resulted in making a destructor-microorganisms collection from the ISS board, which as of today numbers about 300 cultures. Among them, about 30 cultures of technophile microorganisms were identified and 17 species of mycelian and 1 species of yeast fungi, 7 bacteria genus and 3 actinomycete genus were discovered.

All discovered species are cosmopolitan microorganisms. Their natural habitat is soil, however, they have also coped with materials related to human activity. Such microorganisms are able to cause bio-injuries to various polymeric materials and to accelerate metal corrosion. Besides, many of them are able to form dangerous toxins, thus provoking allergy and lung diseases. These microorganism species are known as background ones or very frequent ones in apartments and offices.

Besides identification of specific composition of “unpleasant neighbors” inhabiting the ISS, the Moscow researchers also evaluated the educed cultures ability to cause corrosion of aluminium-magnesium alloy, which the station body is made of. To this end, the researchers used cylindrical billets made of the same alloy, which they exposed to the so-called biocorrosion load with involvement of cosmic destructor microorganisms’ cultures, and then, with the help of various contemporary microscopy methods – exposed to scanning electronic, atomic-powered and raster electronic load and assessed the metal damage level.

The most active biocorrosion agents turned out to be Aspergillus flavus, Aspergillus niger – mold fungi, which grow in nature on grains with increased content of oil of yellow and black color, respectively, as well as Cladosporium herbarum, a fungus causing leaf mold to cruciferous. Having settled on metal, these fungi caused deep pitting of the alloy sample surface, the action of other microorganism species caused less damage to it, as well as appearance of stains and scum. However, it should be noted that the modeling experiments created the most favorable conditions for microorganism development, namely – increased temperature and cell concentration. Thus, within a year of their destructive activity, microorganism managed to destroy the alloy surface for the depth of 43 microns. However, it is not worth raising the alarm immediately: if the experiments results are carried over to real conditions of the MSS operation, then, according to the researchers’ calculations, the dangerous depth of microorganisms injury to the station body may be achieved within 30 years at the earliest.

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