International Space Station Internal Environments (ISS Internal Environments) - 08.16.17

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Evaluation of the International Space Station Internal Environment (ISS Internal Environment) from air, water and surface samples of International Space Station (ISS) provided a baseline of the contaminant characterization onboard the ISS. All of the partner agencies recognize the importance of crew health to mission success and are dedicated to maintaining the health of all crewmembers throughout all phases of ISS missions.   The data obtained from Environmental Monitoring provides insight into the environmental contamination during the stages of construction and habitation of ISS.
Science Results for Everyone
Closed environments, like the space station are easily contaminated. Regular testing of its air, water and surfaces contribute to many studies aimed at ensuring crew safety. These results indicate cleaning protocls developed based on lessons learned from Mir and Skylab have been effective in making ISS a safe place to live and work.  These efforts to keep the crew safe will continue through the life of the station.

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Experiment Details


Principal Investigator(s)

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Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)

Research Benefits
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ISS Expedition Duration

Expeditions Assigned
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Previous Missions
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Experiment Description

Research Overview

  • The closed environment of the International Space Station must be monitored for contamination to ensure the health of the crew living and working on ISS.
  • Contamination of the ISS environment can be caused by off-gassing of vapors from items (plastics, tape, etc.), as well as microbes (bacteria and fungi) growth inadvertently carried to ISS on the crew and supplies.
  • Testing of the air, water and surface of ISS for contaminants will alert the crew of a significant increase in contaminant particles on ISS. The crew can change out the air filters, clean surfaces and treat the water on ISS to prevent illness from the increased contaminants.
  • Experience in monitoring the ISS environment provides a new understanding of the closed environment and will be applied to operations of future spacecraft.


To successfully live and work in the environment of space, the ISS environment must be monitored and kept within the guidelines set forth by the International Space Station Medical Operations Requirement Document  to ensure the health of the crew living and working there. Astronauts can be more sensitive to air pollutants because of the closed environment. Pollutants in this environment are magnified in ISS because the exposure is continuous.

Sources of physical, chemical, and microbiological contaminants include humans and other organisms, food, cabin surface materials and experiment devices. One hazard is the off-gassing of vapors from plastics and other items on ISS; although this is a small hazard, the accumulation of these contaminants in the air can prove dangerous to crew health. The air sampling systems on ISS periodically checks the air for potential hazards. The U.S. segment utilizes advanced high efficiency particulate air (HEPA) filters and periodically participates in filter cleanings to keeping harmful vapors out of the air. The Russian segment uses pleated woven filters to maintain low microbial levels. Both the HEPA filter and the woven sheets have proven to reduce the number of dust particles and microorganisms aboard the ISS.  Other significant contaminants that pose hazards to the crew are microbial growth, both bacterial and fungal; air, water and surface sampling by the crew in conjunction with periodic cleaning keep the microbial levels on ISS in check.

The volatile organic analyzer (VOA) is an atmospheric analysis device on ISS that uses a gas chromatograph and ion mobility spectrometer to detect, identify, and quantify a selected list of volatile organic compounds (i.e., ethanol, methanol and 2-propanol) that are harmful to humans at high levels in a closed environment, such as ISS. The ISS also utilizes  the POTOK air filtration device employed by Roscosmos to disinfect and inactivate microorganisms by electrostatic pulses and charged ions.

To monitor microbial levels on ISS crewmembers use devices called grab sample containers, dual absorbent tubes and swabs to collect station air, water and surface samples and send them to Earth for detailed analysis and identification every 6 months. This data provides controllers on Earth detailed information about the type of microbial contaminants on board ISS. The controllers can then give direction to the crew on sanitation if increased microbial growth is identified. The crew keeps microbes under control on ISS through periodic scheduled sanitation of the ISS.

Missions to beyond low Earth orbit will increase the length of time that astronauts live and work in closed environments. To complete future long-duration missions the crews must remain healthy in closed environments, hence future spacecraft must provide sensors to monitor environmental health and accurately determine and control the physical, chemical and biological environment of the crew living areas and their environmental control systems.

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Space Applications
Environmental Monitoring is vital to ensuring crew and spacecraft health during space flight. The results are being used to identify specific effects of a closed space environment on astronauts. This knowledge will allow scientists to develop systems to enable the crew to remain health on future long duration missions to the Moon and Mars.

Earth Applications
Increased understanding of the affects of a closed space environment on humans will increase the knowledge of living in extreme conditions such as submarines or the artic. Due to widespread growth in the use of colloidal silver as a biocidal agent, develop of a simple and cost efficient method of silver testing is valuable.

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Operational Requirements and Protocols

Numerous air, water and surface samples are collected by ISS crews on a regular basis. Many of these samples are cultured on board ISS while others are preserved and returned to Earth for later analysis. These samples are analyzed using the following methods on board ISS:

  • Archival - The crew collects a sample and returns it to Earth for analysis. To complete this type of analysis the following tools are used:
    • grab-sample canisters that capture about a fist-sized volume of air
    • formaldehyde badges that trap the formaldehyde in a matrix
    • dual sorbent tubes that trap many pollutants in a matrix
  • Real-Time - The crew collects and analyzes the sample on ISS. To complete this type of analysis the following tools are used:
    • Compound Specific Combustion Product Analyzer - looks at potential toxic products of combustion, such as a fire, onboard the spacecraft and analyzes carbon monoxide, hydrogen cyanide, hydrogen chloride, and oxygen particles in the air
    • Volatile Organic Analyzer (VOA) - uses gas chromatography/ion mobility spectrometry to isolate volatile compounds in the ISS atmosphere daily
    • Major Constituent Analyzer - monitors the ISS atmosphere continuously for oxygen, nitrogen, carbon dioxide, hydrogen, methane, and water vapor levels.
    • Microbial Air Sampler- U.S. supplied air sampler
    • Ecospherea Kit- Russian supplied air sampler
    • Water Microbiology Kit- U.S. supplied water sampler

The crew utilizes handheld equipment to monitor the air, water and surfaces of ISS on a daily, weekly and monthly basis. The samples can be returned to Earth for analysis by scientists. Other automated equipment, including the VOA and,  the Major Constituent Analyzer monitor the atmosphere of ISS daily for potential harmful contaminants. The crew also performs weekly housekeeping duties on board ISS, which includes disinfecting surfaces and cleaning air filters which contributes to environmental monitoring.

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Decadal Survey Recommendations

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Results/More Information

During one study of the ISS atmosphere, 12 bacterial strains were isolated and fingerprinted from the ISS water system. These bacteria consisted of common strains and were encountered at levels below 10,000 colony-forming units/10 cm2, which is well below the minimum of bacteria needed to cause illness. These data represent the beginning of ISS habitation and indicate that the lessons learned from previous Mir and Skylab missions were implemented and have been effective in keeping station a safe place in which to live and work (Castro et al. 2004).

Solid-waste treatment in space must be safely processed and stored in a confined environment. Most of the solid-waste is wet and therefore poses a high risk of culturing the growth of undesirable microorganisms. Analysis was performed in order to assess potential crew risks resulting from microbial decay. Results show certain levels of volatile organic compounds, ethylene, methane and carbon dioxide. These gases are being contained within the trash compartments, therefore minimalizing potential risk for crewmembers (Peterson et al 2004).

In comparison to previous identification techniques, scientist decided to test additional sampling and detection methods on station. Previously, samples were limited to conventional culture-dependent methods. Now, scientist looked at specific biomarkers, such as ATP and DNA, to help identify non-culturable species. Samples were collected from several different surfaces along with drinking water reservoirs. Culture-dependent samples identified different species of Bacillus, while culture-independent techniques revealed a whole array of different microbes, previously not identified. Once samples were returned to Earth, further DNA analysis confirmed the findings including certain opportunistic pathogens with all levels within the accepted range. This study supports the idea of utilizing multiple detection techniques to completely identify all microbes present on the ISS (La Duc 2004).

Another study performed an in-depth microbial examination of the drinking water in various stages (from the NASA Kennedy Space Center, Cape Canaveral, FL to the ISS ports). These studies have revealed that NASA policy for biocide treatment has effectively removed pathogenic microbes prior to ingestions by crew members (La Duc 2004). Further analysis of samples collected from station noted the reoccurring presence of Ralstonia eutropha, Methylobacterium fujisawaense, and Psuedomonas aeruginosa in the potable water system. Certain counts were above the acceptable limit, calling for supplementary antimicrobial attention. Additional in-flight monitoring for the specific detection of coliforms (bacteria typically indicative of food contamination) was also introduced (Bruce et al 2005).

The following year, additional water samples were returned for ground examination. Analysis revealed the presence of nucleic acids belonging to various pathogens, but no viable pathogens were recovered. Air and surface samples were also analyzed for microbial characterization. Concentrations of airborne bacteria and fungi were within the accepted range, with a predominant concentration of Staphylococcus, Aspergillus and Penicillium. Surface samples rarely exceeded the acceptable limit, with increased concentrations of Staphylococcus, Aspergillus and Caldosporium (Novikova et al 2006).

After a population of microorganisms of 500,000 to 1 million CFU/100 ml was identified in a flex hose assembly, it was brought back to Earth for further analysis. Studies focused on determining if a biofilm formed on certain parts of the assembly. Analysis revealed that the nickel hydroxide and nickel phosphates acted as a barrier to additional biofilms in the flex hose assembly and the SPCU heat exchanger. There are other parts that do not come in contact with these additional protectants, and are potentially the culprit of such high microbial concentrations.  Continued studies must be performed to ensure zero biolfilm formation to maintain the integrity of the water system aboard the ISS (Roman et al 2006).

On station, silver is used as a biocidal agent based on its antimicrobial properties in the potable water system. Recent studies have shown the possible toxicity of colloidal silver to humans, including crew members aboard the ISS. Researchers are currently developing and testing a simple technique that will enable crew members to test silver levels in the water system in less than two minutes (Hill et al 2010).

Continued monitoring has marked the ISS a microbiologically safe working and living habitat. Microbial contamination levels are generally below the required standards with occasional escalations in contamination levels. These increases could be minimized with further developed technologies, specifically with online detection tools that offered simultaneous quantification and identification (Van Houdt et al 2011).

Another area of particular interest deals with the growth of microbial organisms on space-generated solid waste. Once trash was returned to Earth, it was weighed and categorized into personal hygiene waste (56%), drink (11%) and food (18%) waste, plastic waste (12%) or office waste (3%). Station trash has an abundant amount of biodegradable compounds that can aid the growth and proliferation of microorganisms. After ground analysis, several microbes typical of human’s normal flora were identified along with certain pathogenic microbes including Staphylococcus aureus and Escherichia coli. These results can be further utilized to create new criteria for NASA Waste Management Systems (Strayer et al "Characterization" 2012).

Microorganisms recovered from space generated solid waste were processed through a Heat Melt Compactor to determine how efficiently this process eliminated potential threats. Prior to melting trash, specific markers indicative of spore forming bacteria marked the trash to indicate the survival rate of the microbes after the melting process. Post melting, the samples were run though microbial character analysis. Results indicate that this sanitization technique greatly reduced the number of viable microbes, but did not eliminate entirely.  Interior samples were also analyzed, resulting in similar results, indicating this technique efficient in eradicating active microbial growth (Strayer et al "Microbial" 2012).

Continual efforts to ensure crew safety will accompany the lifetime of the ISS. A new type of air testing was performed in 2010, evaluating threshold (T) values for sixteen adverse health effect groups. All T levels were within the safe limit. The highest values were found in mucosal limits, headaches, central nervous system depression, and cardiac sensitization. This evaluation is an integral tool of NASA’s Lifetime Surveillance of Astronaut Health (James et al 2012).

Samples collected from the International Space Station (ISS) and two cleanrooms at the Jet Propulsion Laboratory (JPL) were analyzed to estimate the bacterial populations. The results provide strong evidence that microorganisms normally found on human skin make a substantial contribution to the ISS microbial community, which is not the case in Earth-based cleanrooms. The results obtained assist future studies to determine how stable the ISS bacterial presence is over time. The present results also demonstrate the value of measuring viable cell diversity and population size at any sampling site. This information can be used to identify areas that can be targeted for more stringent cleaning, and allow comparisons with other built sites and help future improvements on the ISS environment to better protect astronaut health (Checinska et al. 2015).

NASA regularly performs ground-based off-gas tests (OGTs), which allow prediction of accumulated volatile pollutant concentrations at first entry on orbit, on whole modules and vehicles scheduled to connect to the International Space Station (ISS). These data guide crew safety operations and allow for estimation of ISS air revitalization systems impact from additional pollutant load. Since volatiles released from vehicle, module, and payload materials can affect crew health and performance, prediction of first ingress air quality is important. To assess whether toxicological risk is typically over or under predicted, OGT and first ingress samples from 10 vehicles and modules were compared. Tested values and Spacecraft Maximum Allowable Concentrations were used to predict total toxicity values (T-values) at first entry. Results were also compared by compound. Frequently over predicted was 2-butanone), whereas propanal and ethanol were typically under predicted, but T-values were not substantially affected. As expected, the predicted T-values were conservative (higher than the actual ingress values) for SpX-D, SpX-1, SpX-3, Orb-1, Lab, MPLM-1, and Node-1; however, the actual T-values for Orb-D, Node 2, and Node 3 were under predicted. No clear trends were apparent when Delta T (DT) was plotted by number of days between OGT and hatch opening. Likewise, there was no significant association between DT vs. time between sample collection or percentage vehicle loading (Romoser et al. 2017).

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Results Publications

    Romoser AA, Scully RR, Limero TF, De Vera V, Cheng PF, Hand JJ, James JT, Ryder VE.  Predicting air quality at first ingress into vehicles visiting the International Space Station. Aerospace Medicine and Human Performance. 2017 February 1; 88(2): 104-113. DOI: 10.3357/AMHP.4702.2017.

    Macatangay AV, Perry JL, Belcher PL, Johnson SA.  Status of the International Space Station (ISS) Trace Contaminant Control System . SAE International Journal of Aerospace. 2011; 4(1): 48-54. DOI: 10.4271/2009-01-2353.

    Aguilera T, Perry JL.  Root Cause Assessment of Pressure Drop Rise of a Packed Bed of Lithium Hydroxide in the International Space Station Trace Contaminant Control System. SAE International Journal of Aerospace. 2011; 4(1): 291-298. DOI: 10.4271/2009-01-2433.

    Novikova ND, De Boever , Poddubko SV, Deshevaya EA, Polikarpov NA, Rakova , Coninx , Mergeay M.  Survey of environmental biocontamination on board the International Space Station. Research in Microbiology. 2006; 157: 5-12. DOI: 10.1016/j.resmic.2005.07.010.

    Peterson BV, Hummerick ME, Roberts MS, Krumins , Kish , Garland JL, Maxwell , Mills .  Characterization of microbial and chemical composition of shuttle wet waste with permanent gas and volatile organic compound analyses. Advances in Space Research. 2004; 34: 1470-1476. DOI: 10.1016/j.asr.2003.11.005.

    Rehnberg L, Russomano T, Falcao FP, Campos F, Evetts SN.  Evaluation of a Novel Basic Life Support Method in Simulated Microgravity. Aviation, Space, and Environmental Medicine. 2011 Feb; 82(8): 104-110. DOI: 10.3357/ASEM.2856.2011.

    Checinska Sielaff A, Probst AJ, Vaishampayan PA, White JR, Kumar D, Stepanov VG, Fox GE, Nilsson HR, Pierson DL, Perry JL, Venkateswaran KJ.  Microbiomes of the dust particles collected from the International Space Station and Spacecraft Assembly Facilities. Microbiome. 2015; 3(1): 50. DOI: 10.1186/s40168-015-0116-3. PMID: 26502721.

    Swanson GT, Cassell AM.  Micrometeoroid and Orbital Debris Impact Damage Recording System. 2011 IEEE Aerospace Conference, Big Sky, MT; 2011 Mar 5-12

    Van Houdt R, Mijnendonckx , Leys N.  Microbial Contamination Monitoring and Control During Human Space Missions. Planetary and Space Science. 2012 Jan; 60(1): 115-120. DOI: 10.1016/j.pss.2011.09.001.

    Bobe L, Samsonov N, Gavrilov L, Novikov V, Tomashpolskiy M, Andreychuk P, Protasov N, Synjak Y, Skuratov .  Regenerative water supply for an interplanetary space station: The experience gained on the space stations "Salut", "Mir", ISS and development prospects. Acta Astronautica. 2007; 61: 8-15. DOI: 10.1016/j.actaastro.2007.01.003.

    Wheeler RM.  Plants for Human Life Support in Space: From Myers to Mars. Gravitational and Space Biology. 2010; 23(2): 25-36.

    Bruce RJ, Ott CM, Skuratov , Pierson DL.  Microbial Surveillance of Potable Water Sources of the International Space Station. Environmental Systems and European Symposium, Rome Italy; 2005

    Garcia HD, Tsuji JS, James JT.  Establishment of exposure guidelines for lead in spacecraft drinking water. Aviation, Space, and Environmental Medicine. 2014 July; 85(7): 715-720. DOI: 10.3357/ASEM.3853.2014.

    La Duc MT, Summer R, Pierson DL, Venkat P, Venkateswaran KJ.  Evidence of pathogenic microbes in the International Space Station drinking water: reason for concern?. Habitation. 2004 January 1; 10(1): 39-48. DOI: 10.3727/154296604774808883. PMID: 15880908.

    Zanardini L, Steffen S.  Columbus cabin heat exchanger dry out during ISS high beta angle phase. SpaceOps 2014, Pasadena, CA; 2014 May 5-9 12 pp.

    Checinska Sielaff A, Kumar RM, Pal D, Mayilraj S, Venkateswaran KJ.  Solibacillus kalamii sp. nov., isolated from a high-efficiency particulate arrestance filter system used in the International Space Station. International Journal of Systematic and Evolutionary Microbiology. 2017 April; 67(4): 896-901. DOI: 10.1099/ijsem.0.001706. PMID: 28475026.

    La Duc MT, Venkateswaran KJ.  Microbial Monitoring of Spacecraft and Associated Environments. Microbial Ecology. 2004 02/01/2004; 47(2): 150-158. DOI: 10.1007/s00248-003-1012-0. PMID: 14749906.

    Castro VA, Thrasher AN, Healy M, Ott CM, Pierson DL.  Microbial Charcterization during the Early Habitation of the International Space Station. Microbial Ecology. 2004; 47: 119-126. DOI: 10.1007/s00248-003-1030-y.

    Castro VA, Thrasher AN, Healy M, Ott CM, Pierson DL.  Microbial Characterization during the Early Habitation of the International Space Station. Microbial Ecology. 2004; 47: 119-126. DOI: 10.1007/s00248-003-1030-y.

    Green RD, Agui J, Berger GM, Vijayakumar R, Perry JL.  Filter efficiency and pressure testing of returned ISS bacterial filter elements (BFEs). 47th International Conference on Environmental Systems, Charleston, South Carolina; 2017 July 16-20 7 pp.

    Hill , Lipert , Porter MD.  Determination of colloidal and dissolved silver in water samples using colorimetric solid-phase extraction. Talanta. 2010; 80(5): 1606-1610. DOI: 10.1016/j.talanta.2009.09.056.

    James JT, Zalesak .  Prediction of Crew Health Effects from Air Samples Taken Aboard the International Space Station. Aviation, Space, and Environmental Medicine. 2012; 83(8): 795-799. DOI: 10.3357/ASEM.3337.2012.

    Schiwon K, Arends K, Rogowski KM, F├╝rch S, Prescha K, Sakine T, Van Houdt R, Werner G, Grohmann E.  Comparison of Antibiotic Resistance, Biofilm Formation and Conjugative Transfer of Staphylococcus and Enterococcus Isolates from International Space Station and Antarctic Research Station Concordia. Microbial Ecology. 2013 April; 65(3): 638-651. DOI: 10.1007/s00248-013-0193-4. PMID: 23411852.

    Mora M, Mahnert A, Koskinen K, Pausan MR, Oberauner-Wappis L, Krause R, Perras AK, Gorkiewicz G, Berg G, Moissl-Eichinger C.  Microorganisms in confined habitats: Microbial monitoring and control of intensive care units, operating rooms, cleanrooms and the International Space Station. Frontiers in Microbiology. 2016 October 13; 7: 1573. DOI: 10.3389/fmicb.2016.01573. PMID: 27790191.

    Monsieurs P, Mijnendonckx , Provoost A, Venkateswaran KJ, Ott CM, Leys N, Van Houdt R.  Draft genome sequences of Ralstonia pickettii strains SSH4 and CW2, isolated from space equipment. Genome Announcements. 2014 September 4; 2(5): e00887-14. DOI: 10.1128/genomeA.00887-14. PMID: 25189592.

    Alekhova TA, Zakharchuk LM, Tatarinova NY, Kadnikov VV, Mardanov AV, Ravin NV, Skryabin KG.  Diversity of bacteria of the genus Bacillus on board of International Space Station. Doklady Biochemistry and Biophysics. 2015 November; 465(1): 347-350. DOI: 10.1134/S1607672915060010. PMID: 26728721. [Original Russian Text © T.A. Alekhova, L.M. Zakharchuk, N.Yu. Tatarinova, V.V. Kadnikov, A.V. Mardanov, N.V. Ravin, K.G. Skryabin, 2015, published in Doklady Akademii Nauk, 2015, Vol. 465, No. 1, pp. 104–107.]

    Strayer , Hummerick ME, Richards JT, McCoy C, Roberts MS, Wheeler RM.  Characterization of Volume F Trash from the Three FY11 STS Missions: Trash Weights and Categorization and Microbial Characterization. 42nd International Conference on Environmental Systems, San Diego, CA; 2012

    Venkateswaran KJ, Vaishampayan PA, Cisneros J, Pierson DL, Rogers SO, Perry JL.  International Space Station environmental microbiome - microbial inventories of ISS filter debris. Applied Microbiology and Biotechnology. 2014 April 4; epub. DOI: 10.1007/s00253-014-5650-6.

    Ichijo T, Hieda H, Ishihara R, Yamaguchi N, Nasu M.  Bacterial monitoring with adhesive sheet in the International Space Station-"Kibo", the Japanese experiment module. Microbes and Environments. 2013 April 20; 28(2): 264-268. DOI: 10.1264/jsme2.ME12184. PMID: 23603802.

    Reddy SY, Frank JD, Iatauro MJ, Boyce ME, Kurklu E, Al-Chang M, Jonsson AK.  Planning Solar Array Operations on the International Space Station. ACM Transactions on Intelligent Systems and Technology. 2011 Jul; 2(4): 41:1-41:24. DOI: 10.1145/1989734.1989745.

    Strayer , Hummerick ME, Richards JT, McCoy C, Roberts MS, Wheeler RM.  Microbial Characterization of Space Solid Wastes Treated with a Heat Melt Compactor. 42nd International Conference on Environmental Systems, San Diego, CA; 2012

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Ground Based Results Publications

    Bechy-Loizeau A, Flandrois J, Abaibou H.  Assessment of polycarbonate filter in a molecular analytical system for the microbiological quality monitoring of recycled waters onboard ISS. Life Sciences in Space Research. 2015 July; 6: 29-35. DOI: 10.1016/j.lssr.2015.06.002.

    Willsey GG, Wargo MJ.  Extracellular lipase and protease production from a model drinking water bacterial community is functionally robust to absence of individual members. PLOS ONE. 2015 November 23; 10(11): e0143617. DOI: 10.1371/journal.pone.0143617. PMID: 26599415.

    Mijnendonckx , Provoost A, Ott CM, Venkateswaran KJ, Mahillon J, Leys N, Van Houdt R.  Characterization of the Survival Ability of Cupriavidus metallidurans and Ralstonia pickettii from Space-Related Environments. Microbial Ecology. 2012 12/05/2012; epub. DOI: 10.1007/s00248-012-0139-2. PMID: 23212653.

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ISS Patents

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Related Publications

    Wallace W, Gazda DB, Limero TF, Minton JM, Macatangay AV, Dwivedi P, Fernandez FM.  Electrothermal vaporization sample introduction for spaceflight water quality monitoring via gas chromatography-differential mobility spectrometry. Analytical Chemistry. 2015; epub. DOI: 10.1021/acs.analchem.5b00055. PMID: 25971650.

    Devarayan K, Sathishkumar Y, Lee YS, Kim B.  Effect of microgravity on fungistatic activity of an α-aminophosphonate chitosan derivative against Aspergillus niger. PLOS ONE. 2015 October 15; 10(10): e0139303. DOI: 10.1371/journal.pone.0139303. PMID: 26468641. [supported by National Research Foundation of Korea.]

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