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Biocontamination in spacecrafts

Microorganisms are part of the natural human biota, and are also residents of soil, water and air on Earth. Microbes are also found in hermetically-sealed space crafts, and are in fact constant ecological partners of humans during manned space flight (Novikova et al. 2001). During many years of the MIR space station operations, bacteria and fungi would frequently be found within the environment, primarily on the construction materials of the interior and the hardware (Novikova et al. 2004). In the process of long-term operations of the International Space Station, research has been regularly carried out to study the quantitative content and species composition of the microorganisms forming in the crew compartments. A total of 80 species of microorganisms have been found in the environment of the orbital complex, 41 species of which were bacteria, and 39 species of which were fungi.

In the course of manufacturing, storage and transportation, and during operation instruments and devices can be easily contaminated by microorganisms. As for the traditional types of human activity, general scenarios of microbial damage of objects created or controlled by humans have been identified. From the wealth of facts accumulated by Russian and foreign investigators an eco-technological concept of biodamage has been formulated. According to this concept, on the one hand, biodamage is, in one way or another, related with (or portray of) the environment. On the other hand, biodamage can be considered an anthropotechnical phenomenon, for which the human presence and the products of this activity is the basic condition for biodamage. Hence, based this concept, it can be concluded in fact biodamage is rather a two- than a one-way process. In view of the earlier described principle characteristics of microorganisms, their biology and ecology, these agents are able to inflict bad damage to hardware and associated technologies. On the other side, in a broad sense the hardware in itself (as a product of human activity as well as technologies) can bring about profound and even irreparable changes in the most important phenotypic and genotypic characteristics of microorganisms on both subpopulation and population levels.

Operational conditions in space crafts are set to keep microbial levels in air and on surfaces low. In the ISS, the threshold of biocontamination in the air is being set to 1000 CFU/m3 for bacteria, and 100 CFU/m3 for fungi, according to the technical document Medical Operations Requirements Documents (ISS MORD SSP 50260). Studies have indeed shown that less than 500 CFU/m3 were found for 95% of samples, although higher numbers were found with a maximum of 710 CFU/m3 in the ISS and even of 3530 CFU/m3 in the Mir station (Novikova et al. 2004; Novikova et al. 2006), the difference rate fungi/microbes achieved 1/100). On surfaces, limits are maintained as 100 CFU/100 cm2 for fungi and 10000 CFU/100cm2 for bacteria. Actually the amount of bacteria and fungi 10 times increases the maintained level & results for surfaces. Humidity can increase the biocontamination problems on surfaces.

However, the low numbers of microorganisms may not exclude a potential risk.

Some species of microorganisms, most often bacterial-fungal associations, can rapidly accommodate on various materials (for example, polymers) and start proliferating. These so called technophilic bacteria and fungi colonise the infrastructure and equipment and play a particular role in adding to technical risks. These microorganisms, through their life activity, are able to cause biointerference in hardware functioning, degrade various structural materials including synthetic polymers, produce or provoke corrosion of metals. This may result in change in colour, deterioration of mechanic strength, dielectric and other properties.

Development and growth of fungi (bacteriofungal associations) results in destruction of polymers. Mechanic damage to polymers occurs due to penetration of fungal mycelium into the structure of materials; direct biodamage is consequent to establishment of trophic relations between material components and micromycets; indirect biodamage is an effect of exo-enzymes and organic acids produced by microorganisms. It must be emphasized that microorganisms developing on polymers can emit volatile toxic compounds as products of polymer biodegradation (Novikova 2002). Accumulation of these compounds on polymers can impair sanitary/hygienic properties of polymers and lead to air contamination by harmful trace contaminants (Novikova 2002). Meanwhile spore forming Bacillus & Penicillium sp. are dominant and important environmental microorganisms involved in biodegradation.

Microbial corrosion of metals may follow independently or accompany electrochemical and other types of corrosion. Biocorrosion of metals by fungi is secondary by nature as they are heterotrophs and need organic compounds for development. First fungi make home and develop on organic contaminants of metals; later on, mycelium popularizes and its metabolites – acids and enzymes – corrode metals. Metallic corrosion is primarily caused by exometabolites of microorganisms – mineral and organic acids, bases, enzymes etc. They create corrosion-active medium and in the presence of water corrosion goes by general laws of electrochemistry. Colonies of microorganisms are able to form deposits and films of mycelium or slime on materials with ulcerous (pitting) corrosion developing underneath as a result of voltage on different parts of the metallic surface and assimilation of metallic ions by microorganisms. Expanding on contaminated surfaces, fungal mycelium will retain water even if relative air humidity drops below 60%. Local rise in humidity in the presence of mycelium is another favourable factor for corrosion. Formation of mycelium on the surface of electrical connectors can disturb their function by short-circuiting or disjunction due to corrosive deposits.

The problem of microbial colonization of materials is even more critical when regenerative life support systems are involved, e.g. the systems of water regeneration from air condensate. In water pipes of these systems specific biofilms can appear by way of adhesion and consist of bacteria proper or bacteriofungal associations and the lipoproteid complex (glycocalix) produced by the associations with inclusion of organic and inorganic water components. The films are very stable and impenetrable for many biocides, disinfectants and antibiotics. Utilization of these products brings death only to the so-called “free floating” cells of microbes. However, microorganisms encased in the biofilm intima survive and reappear shortly in the environment. Specific hazardous situations may arise in the event of colonization of the interior and equipment of pressurized space modules by bacteriofungal associations that have undergone phenotypic and genotypic adaptation and formed a peculiar ecosystem or biodamaging consortium of microorganisms of which the aggressiveness and resistance is much higher and different from natural properties of individual member species (Ilyin V.K. 2005 et al.).

In fact, as a result of their metabolic processes, microbes are capable of causing biodeterioration of polymers and biocorrosion of metals in the MIR station (Novikova et al. 2004). At the same time, the formation of specific reservoirs of microorganism aggregation and reproduction has been noted in specific areas in the MIR station, leading to a number of cases where there was a negative impact on operations and even the failure of various equipment (Novikova et al. 2006). Methylobacterium exotorquens and Delftia acidovorans which can colonize and attack various polymeric or metallic surfaces were found on board the International Space Station in a survey of the environmental biocontamination (Novikova, 2006).

Existence of microorganisms in the space vehicle environment induces also serious medical risks.  Bacterial-fungal associations will occupy the decorative-finish and structural materials of the interior and equipment. Involvement of human pathogens in this process may lead to formation of reservoirs of agents of infections on the type of sapronoses (organism living on the organic material of other dead organism), often found for fungi. Participation of human pathogens – fungi (Aspergillus niger and others) and bacilli (Pseudomonas aeruginosa) - in biodegradation of materials can gravely impact the situation by adding medical risks to technical. This may lead to the precondition sensitization of the crew and development of allergic reactions, mycoses, and mycotoxications in crew members. In the interior and on equipment of the habitable modules there occasionally appeared zones where concentrations of opportunistic pathogenic bacilli and fungi rose as high as 106 or more CFU/100 cm2 (Novikova 2006). Several (opportunistic) pathogens such as Stenotrophomonas maltophilia, Ralstonia paucula, C. guilliermondii and C. krusei were identified from condensate accumulated on panels on board the Mir Space Station (Ott, 2004). Staphylococcus sp. (especially S.aureus and even meticillin resistant Staphylococcus epidermidis) and Pseudomonas aeruginosa are dominant and important medically relevant bacterium involved in biocontamination (Ilyin V.K. 2005 et al).

Microbes have also the capacity to directly engage interactions with the human body– ranging from forms of symbiosis (as mutualism) to parasitism and infectious disease (Novikova et al. 2002). Based on results of clinical/physiological investigations of cosmonauts, permanent medical risks from the shifts in crew microflora in space are:

  • intestinal disbacterioses (reduction of bifido- and lactoflora),
  • activation of the opportunistic pathogenic component of microflora of various biotopes, e.g. growth of the Staphylococcus aureus population on the nasal, stomatic and fauces mucous coat; infection by Staphylococcus, aureus by way of microflora interchange among crew members; increased titers of Clostridium sp., Proteus sp., Klebsiella sp., and other opportunistic pathogens in intestinal microflora (Ilyin V.K. 2005et al.)
  • translocation onto the mucous coat of the nose, mouth and fauces onto integument of atypical microorganisms for these biotopes,e.g. Klebsiella, Enterobacter, Proteus, Escherichia coli, and Staphylococcus aureus on various parts of the skin, (Ilyin V.K. et al.).
Transmission of the most dangerous infections in the space cabin during pre-flight preparation, assembly and operation of space complex in near-Earth orbit, will lead to an emergency termination of the mission. Hypothetically these cases can result from badly-designed or insufficient methods of clinical/physiological, microbiological and immunologic investigations of crew members (asymptomatic carriage of infection, latent infection, incubation period or prodromic state), pre-launch social restraint-and-observation and quarantine applied to equally the crew and the launch personnel, quality control of space food and water supplies, sanitary-hygienic procedures of pre-flight verification of the systems of life support, thermal control, etc.

In addition, during spaceflight micro-organisms adapt to the specific environmental conditions. Space specific conditions such as altered gravity and radiation may have an impact. Microgravity experiments, in space or simulated on Earth on different bacteria have shown that altered gravity may directly or indirectly affect their growth and microbial metabolism and physiology, as for example increasing their resistance and virulence both in planktonic and biofilm mode of growth (Matin, 2006: Wilson et al., 2008; Crabbé et al., 2008; Mastroleo et al. 2009; Leys et al. 2009). The chronic exposure to the higher doses of ionising radiation in space can also influence the microbial metabolism and physiology (Mastroleo et al. 2009). These space environmental conditions thus can lead to the development of new traits and increase the possible related risk for the crew both for their health and in terms of degradation of their environment, including the stability of life support systems.  

Hence, these data clearly demonstrate the possibility of medical and technical risks associated with biocontamination aboard manned space vehicles. There is obviously an urgent need to study the specific features relating to the formation and behaviour of microbiota in manned spacecraft, along with an evaluation of the risks associated with the life processes of microorganisms in the environment. Obtaining such data is a necessary condition for creating a science-based system of ecological monitoring and antimicrobial protection that will fit present and future space missions (Ilyin et al. 2008). The further scientific researches to be in this field should be concentrated on investigations of the problems of contamination, mainly, from bacterial aerosols, as well as testing of existing means and measures for antimicrobial protection.

 In view of future long-duration spaceflights for exploration, it is mandatory to better understand the underlying mechanisms of biocontamination, to better characterise possible microbial populations, their evolution in these confined environments in relation with human activities, in order to better prevent or limit the possible associated risks for the crew and the overall mission thanks to rational systems designs, adequate sanitary programmes and reliable countermeasures. This effort should rely on optimized predictive models rather than solely on empirical information.

 

 

References

 

  • Novikova N.D., Polikarpov N.A., Poddubko S.V., Deshevaya E.A.(2001). The results of Microbiological Research of Environmental Microflora of Orbital Station MIR // Proceedings of the 31st International Conference on Environmental Systems. July 9-12, 2001, Orlando, Fl., CD # 2001-01-2310.
  • Novikova N.D. Microbiological risks in extended space mission // 11th International Conference “Space Activity and Relevant Insurance Applications”, Rome-March 15-16, 2001. Printed in Italy by Editoriale Ergon s.r.l.- 2002.  P. 245-253.
  • Novikova N.D. Review of the Knowledge of Microbial Contamination of the Russian Manned Spacecraft // Microbial Ecology. 2004. V. 47. No. 2. P. 127-132.
  • Novikova N.D., Patrick De Boever, Svetlana Poddubko, Elena Deshevaya, Nikolai Polikarpov, Natalia Rakova, Ilse Coninx, Max Mergeay. Survey of the environmental biocontamination aboard the International Space Station. // Research in Microbiology.  2006. 157. P. 5-12.
  • Ilyin V., D.Korshunov, N. Chuvilskaya, G.Doronina, R. Mardanov, L. Moukhamedieva, N. Novikova, L. Starkova, E. Deshevaya.  Microbial purification of waste biodegradat liquid products.// Ecological engineering and environment protection. -2008. No 1. P. 48-55.
  • Matin A, Lynch SV, Benoit MR. 2006. Increased bacterial resistance and virulence in simulated microgravity and its molecular basis. Gravitational and Space Biology 19 (2): 31-42.
  • Novikova ND. 2004. Review of the knowledge of microbial contamination of the russian manned spacecraft. Microbial Ecology 47 (2): 127-132.
  • Novikova N.D., De Boever P, Poddubko S, Deshevaya E, Polikarpov N, Rakova N, Coninx I, Mergeay M. 2006. Survey of environmental biocontamination on board the International Space Station. Research in Microbiology 157 (1): 5-12.
  • Ott CM, Bruce RJ, Pierson DL.  2004. Microbial characterization of free floating condensate aboard the Mir space station. Microbial Ecology 47(2): 133-136.
  • Leys N, Baatout S, Rosier C, Dams A, s'Heeren C, Wattiez R, Mergeay M: The response of Cupriavidus metallidurans CH34 to spaceflight in the international space station. Antonie Van Leeuwenhoek 2009, 96:227-245.
  • Mastroleo F, Van Houdt R, Leroy B, Benotmane MA, Janssen A, Mergeay M, Vanhavere F, Hendrickx L, Wattiez R, Leys N: Experimental design and environmental parameters affect Rhodospirillum rubrum S1H response to space flight. ISME J 2009.
  • Crabbe A, De Boever P, Van Houdt R, Moors H, Mergeay M, Cornelis P: Use of the rotating wall vessel technology to study the effect of shear stress on growth behaviour of Pseudomonas aeruginosa PA01. Environ Microbiol 2008, 10:2098-2110.
  • Wilson JW, Ott CM, Quick L, Davis R, Honer zu Bentrup K, Crabbe A, Richter E, Sarker S, Barrila J, Porwollik S, et al: Media ion composition controls regulatory and virulence response of Salmonella in spaceflight. PLoS One 2008, 3:e3923.
  • Novikova N.D. 2002 Microbiological risks in extended space mission // 11th International Conference “Space Activity and Relevant Insurance Applications”, Rome-March 15-16, 2001. Printed in Italy by Editoriale Ergon s.r.l.: 245-253.
  • Novikova N.D. 2006. Microbiological Safety Maintenance of the Mission. In: Manned Mission to Mars // Edited by A.S.Koroteev. – M.: Russian Academy of Cosmonautics named after K.E.Tsiolkovsky.: 277 – 283.
  • Ilyin V.K. Volozhin A.I., Vikha G.V. Colonial resistance of organism in modified environment. Moscow Nauka 2005? 275 p.