The Microbe experiment will investigate the effects of the space flight environment on virulence (ability to infect) of three model microbial pathogens: Salmonella typhimurium, Pseudomonas aeruginosa, and Candida albicans, that have been identified as potential threats to crew health based upon previous space flight missions.Principal Investigator(s)
NASA Ames Research Center, Moffett Field, CA, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration
April 2006 - September 2006Expeditions Assigned
13Previous ISS Missions
Yeast-GAP, a similiar investigation to Microbe was initially performed on ISS Expedition 8.
A human presence in space, whether permanent or temporary, is accompanied by the presence of microbes. The extent of changes to microorganisms in response to space flight conditions is not completely understood. Because the length of human space missions is increasing, there is an increased risk to orbiting humans of infectious disease
events occurring inflight. Previous studies have indicated that space flight weakens the immune system in both
humans and animals. As astronauts and cosmonauts live for longer periods in a closed environment and using
recycled water and air, there is an increase in the potential for negative impacts of microbial contamination upon the
health, safety, and performance of crewmembers. Therefore, understanding how the space environment affects
microorganisms and their disease causing potential is critically important for space flight missions and requires
The Microbe experiment employed three model microbes, Salmonella typhimurium, Pseudomonas aeruginosa, and Candida albicans to examine the global effects of space flight on microbial gene expression and virulence attributes. These represent different types of bacteria and yeast. Salmonella is the most common agent for gastroenteritis in humans. Sanitation procedures are used to eliminate Salmonella from food sent to orbit, but if some were missed, the impact on crew health could be significant. Pseudomonas has been detected as a contaminant in the water system of spacecraft, and was once a cause of crewmember infection during the Apollo era. Candida is a yeast that is present as part of the natural human flora, but has the potential for harmful overgrowth if microbial communities were to change over time in space.
The experiment was flown inside self-contained culture chambers which can be activated manually by a crewmember turning a hand crank to release growth media into the cell chamber. After 24 hours of growth at ambient temperatures, the growth was stopped by a crewmember turning the hand crank once more. Upon landing, one third of the samples were recovered as soon as possible and the live cells will be used immediately for the virulence studies while the remaining stabilized samples were frozen at minus 80 degrees C. Ground analysis focused on identifying differences in growth rates and patterns, changes in gene expression, and changes in virulence of the microbes in space compared to Earth.
By understanding the changes that microorganisms undergo in the space environment, these studies may lead to the development of vaccines and other novel countermeasures for the treatment and prevention of infectious diseases occurring during space flight and on Earth.
Results from this single flight experiment will provide important information on the threat of pathogens in the space environment, which will assist with development of diagnostic tools to monitor the atmosphere, water and surfaces for the presence of these microbes. Understanding the molecular responses of these organisms to space flight is a necessary step that will significantly contribute to development of systems that meet requirements for supplying and storing potable water that is free of microbial contaminants. Furthermore, identification of the changes caused by space flight to genes and proteins will provide novel targets for pharmacological intervention to prevent and control infectious disease, which will ultimately facilitate safe and productive long-term exploration of the Moon and Mars.Earth Applications
By understanding the unique spectrum of microbial genetic and virulence changes induced by space flight, this experiment will yield valuable knowledge leading to advances in vaccine development and other therapeutics for treatment, prevention and control of infectious diseases on Earth as well as in space.
The microbes will be contained in the glass barrel of a Fluid Processing Apparatus (FPA). The FPA is a tube that contains 2 or 3 separate liquids in addition to the sample. The liquid can be introduced to the sample in a controlled order. The FPA is contained in a Group Activation Pack (GAP). The GAP will hold up to 8 FPAs that can be processed simultaneously. For this experiment, a total of 12 GAPs will be used, 6 for Salmonella and 3 each for Pseudomonas and Candida. For activation and termination, the crew will turn a hand crank that has been inserted onto the top of the GAP. Growth of the samples will last 24 hours before the experiment is terminated. Once the samples are on the ground and have been stabilized, they will be frozen at minus 80 degrees C then shipped to the PI laboratory. The growth of some samples will not be terminated and will be maintained as viable cultures at ambient temperature for infection studies.Operational Protocols
The microbes, Salmonella typhimurium, Pseudomonas aeruginosa, and Candida albicans, will be contained in a Fluid Processing Apparatus (FPA). In order to activate the sample, the crew will turn a hand crank that has been inserted onto the top of the GAP which contains the FPAs. This will release the growth media into the samples initiating growth. The samples will grow for 24 hours in ambient conditions. The crew will then turn the hand crank again to introduce another media to terminate the growth. Once the samples have returned to ground, the live cells will be used in virulence studies while the stabilized samples will be frozen to minus 80 degrees C and shipped to the PI laboratory for gene expression studies.
A human presence in space, whether permanent or temporary, is accompanied by the presence of microbes. However, the response of microorganisms to growth during a spaceflight mission is not completely understood. While several spaceflight studies have investigated changes in microbial characteristics when cultured during spaceflight, the Microbe experiment was the first to investigate changes in virulence and gene expression in several microbes that are pertinent to both astronauts and the general public on Earth. The organisms investigated were ,i>Salmonella enterica, Salmonella Typhimurium, Pseudomonas aeruginosa, and Candida albicans.
Within a few hours after return to Earth aboard STS-115, the S. Typhimurium grown in space was used to infect mice to determine the disease causing potential (virulence) of the organism. Mice infected with bacteria cultured in space displayed a decreased time to death and increased percent mortality compared with those infected with ground controls (Wilson et al 2007). To better understand why the spaceflight-grown cultures were more virulent, an analysis of the gene expression was performed. The S. Typhimurium grown in space expressed a total of 167 genes differently compared to the identically grown cultures on Earth. Surprisingly, many genes that are commonly associated with increased virulence were not differentially regulated. Perhaps the most interesting finding was that a regulatory protein, Hfq, appeared to play a role in the alteration in gene expression in response to spaceflight culture. This finding was the first to identify a potential mechanism by which a microorganism was being altered when grown in space. One additional finding was alterations in microbial morphology.
Also aboard grown aboard STS-115 were cultures of P. aeruginosa (Crabbé 2011). A comparison of spaceflight grown cultures to those grown identically on Earth indicated that 167 genes were differentially regulated, with many being different than those seen with S. Typhimurium. However, one key similarity was that when analysis of the data was performed, Hfq was again identified as a key regulator for many of the differentially regulated genes. This finding reinforced the role for Hfq in microbial response to spaceflight and also suggested that this response may be evolutionarily conserved between species. The differentially regulated gene expression data also indicated that many P. aeruginosa virulence characteristics may increase in response to spaceflight culture. The results for C. albicans are still being evaluated and prepared for publication.
Both during the preparation for spaceflight experiments and to fully understand the results after the experiment, scientists used spaceflight analogues, like the rotating wall vessel (RWV) and the random position machine (RPM) to mimic spaceflight growth conditions in order to gain insight into the potential behavior P. aeruginosa in microgravity (Nickerson 2004). For Microbe, microarray analysis samples of P. aeruginosa grown in a RWV were compared to samples grown in normal gravity controls (Crabbé 2010).The results revealed an alteration in a regulatory role of the sigma factor AlgU, which consequently led to an increase in production of the extracellular substance alginate. This change in gene regulation and increased production of alginate resulted in an increase in heat and oxidative stress resistance. Perhaps most interesting was the involvement of Hfq in response to culture in the RWV, consistent with Microbe spaceflight findings in S. Typhimurium and P. aeruginosa.
The Microbe experiment had far reaching implications. It clarified the mechanisms behind the observations of microbial spaceflight experiments over the past 40 years and initiated studies to understand how these findings impact risk assessment to crew health. In addition, the knowledge gained from space flight research has been the focus of commercial and academic entities toward the discovery of novel therapeutic and vaccine approaches leading to the implementation of new strategies for translation of this research into health benefits for the general public (Sarker et al 2010).
Crabbe A, Wilson JW, Schurr MJ, Nickerson CA, Pierson DL, Morici L, Monsieurs P, Schurr J, Ott CM, Tsaprailis G, Stefanyshyn-Piper H. Transcriptional and Proteomic Responses of Pseudomonas aeruginosa PAO1 to Spaceflight Conditions Involve Hfq Regulation and Reveal a Role for Oxygen. Applied and Environmental Microbiology. 2011; 77(4): 1221-1230. DOI: 10.1128/AEM.01582-10. PMID: 21169425.
Schurr MJ, Wilson JW, Goulart C, Honer zu Bentrup K, Pierson DL, Rupert M, Nickerson CA, Morici L, Stodieck LS, Ramamurthy R, Quick L, Porwollik S, Ott CM, Cheng P, McClelland M, Tsaprailis G, Stefanyshyn-Piper H, Radabaugh T, Hunt A, Fernandez D, Richter E, Shah M, Kilcoyne M, Joshi L, Nelman-Gonzalez MA, Hing SM, Parra MP, Dumars P, Norwood KL, Bober R, Devich J, Ruggles AD, Stafford P, Catella LA, Buchanan K, McCracken J, Allen PL, Baker-Coleman C, Hammond TG, Vogel J, Nelson R. Space flight alters bacterial gene expression and virulence and reveals a role for global regulator. Proceedings of the National Academy of Sciences of the United States of America. 2007; 104(41): 16299-16304. DOI: 10.1073/pnas.0707155104. PMID: 17901201.
Sittka A, Pfeiffer V, Tedin K, Vogel J. The RNA chaperone Hfq is essential for the virulence of Salmonella typhimurium. Molecular Microbiology. 2007; 63(1): 193-217. DOI: 10.1111/j.1365-2958.2006.05489.x. PMID: 17163975.
Wilson JW, Nauman EA, Sander E, Nickerson CA, Pierson DL, Tucker DL, Ott CM. A Novel Quantitative Biosystem to Model Physiological Fluid Shear Stress on Cells. Applied and Environmental Microbiology. 2007 Feb; 73(3): 699-705.
Crabbe A, Van Houdt R, Pycke B, Monsieurs P, Nickerson CA, Cornelis P, Leys N. Response of Pseudomonas aeruginosa to low shear modeled microgravity involves AlgU regulation. Environmental Microbiology. 2010; 12(6): 1545-64.
Sarker SF, Ott CM, Barrila J, Nickerson CA. Discovery of Spaceflight-Related virulence Mechanisms in Salmonella and Other Microbial Pathogens: Novel Approaches to Commercial Vaccine Development. Gravitational and Space Biology. 2010; 23(2): 75-78.
Wilson JW, Pierson DL, Nickerson CA, Ramamurthy R, Ott CM. Microbial Responses to Microgravity and Other Low-Shear Environments. Microbiology and Molecular Biology Reviews. 2004; 68(2): 345-361.
Nickerson CA, Mister SJ, Pierson DL, Morrow BJ, Burns-Keliher L, Ott CM. Microgravity as a Novel Environmental Signal Affecting Salmonella enterica Serovar Typhimurium Virulence. Infection and Immunity. 2000; 68(6): 3147-3152.
Wilson JW, Schurr MJ, Nickerson CA, LeBlanc CL, Ramamurthy R, Buchanan K. Mechanisms of bacterial pathogenicity. Journal of Postgraduate Medicine. 2002; 78(918): 216-224.
Wilson JW, Pierson DL, Nickerson CA, Ramamurthy R, Porwollik S, Ott CM, McClelland M. Low-Shear modeled microgravity alters the Salmonella enterica serovar typhimurium stress response in an RpoS-independent manner. Applied and Environmental Microbiology. 2002; 68(11): 5408-5416. DOI: 10.1128/AEM.68.11.5408-5416.2002.
Wilson JW, Pierson DL, Nickerson CA, Ramamurthy R, Porwollik S, Ott CM, McClelland M, Allen PL, Hammond TG. Microarray Analysis Identifies Salmonella Genes Belonging to Low-Shear Modeled Microgravity Regulon. Proceedings of the National Academy of Sciences of the United States of America. 2002; 99(21): 13807-11382. DOI: 10.1073/pnas.212387899.