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Effect of Spaceflight on Microbial Gene Expression and Virulence (Microbe)
03.22.12

Overview | Description | Applications | Operations | Results | Publications | Images

Experiment/Payload Overview

Brief Summary

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

  • Cheryl A. Nickerson, Ph.D., Arizona State University, Tempe, AZ, United States

    • Co-Investigator(s)/Collaborator(s)

  • C. Mark Ott, Ph.D., Johnson Space Center, Houston, TX, United States
  • Duane L. Pierson, Ph.D., Johnson Space Center, Houston, TX, United States
  • Kent Buchanan, Ph.D., Tulane University Health Sciences Center, Oklahoma City University, Oklahoma, Oklahoma City , OK, United States
  • Michael Schurr, Ph.D., Tulane University Health Sciences Center, University of Colorado, Health Center, Denver, Denver, CO, United States

    • Payload Developer

    Ames Research Center, Moffett Field, CA, United States

    Sponsoring Space Agency

    National Aeronautics and Space Administration (NASA)

    Sponsoring Organization:

    Exploration Systems Mission Directorate (ESMD)

    ISS Expedition Duration:

    April 2006 - September 2006



    Expeditions Assigned

    13

    Previous ISS Missions

    Yeast-GAP, a similiar investigation to Microbe was initially performed on ISS Expedition 8.

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    Experiment/Payload Description

    Research Summary

    • Microorganisms are carried to space on the human body and in water or food. Many organisms that have been identified aboard spacecraft can cause crewmembers to become sick and put a long duration mission at risk.


    • The virulence (disease causing potential) of these microbes can be significantly altered in space due to radiation and microgravity.


    • The Microbe experiment will study three prevalent microbes, Salmonella typhimurium, Pseudomonas aeruginosa and Candida albicans that have been identified as potential threats to crew health based upon previous space flight missions.


    • This evaluation of the effect of space flight on the gene expression and disease causing potential of these microorganisms will identify whether the risk of infection increases as a result of long-duration space flight which is important for the safety and performance during our future Lunar and Martian missions.

    Description

    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 further study.

    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.

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    Applications

    Space Applications

    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.

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    Operations

    Operational Requirements

    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.

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    Results/More Information

    The Microbe experiment was performed in September 2006 during the STS-115/12A mission to the International Space Station (ISS); it tested three microbial pathogens; Salmonella typhimurium, Pseudomonas aeruginosa, and Candida albicans. Initial data from S. typhimurium showed that a total of 167 genes were expressed differently inflight when compared with ground controls. The data indicates that bacteria respond to the microgravity environment with widespread alterations of gene expression (process by which deoxyribonucleic acid, DNA is made into a protein), alterations in microbial morphology (shape and form of microbes) and increased virulence (disease causing potential).

    The changes in gene expression in S. typhimurium indicated that the Hfq protein plays an important role in the response of this organism to the space flight environment; Hfq is a protein that binds to messenger RNA to regulate gene expression, mRNA (creates the blueprint for proteins). Sixty-four genes involved in the expression of Hfq were altered inflight; this is 32 percent of the total genes identified which were expressed differently inflight. In addition, by using a ground-based model of space flight conditions on Earth, it was possible to reproduce the Hfq regulation of some of the Salmonella responses observed in flight. Collectively, these data indicate that Hfq is involved in globally regulating the S. typhimurium space flight response.

    Scanning Electron Microscope (SEM) analysis of S. typhimurium was performed and showed no apparent difference in the size and shape of individual cells in ground samples compared to the space samples. However, the space samples did demonstrate clear differences in microbial morphology as exhibited by the cellular aggregation and clumping that was associated with the formation of an extracellular matrix (provides structural support to increase survival). Because extracellular matrix formation can help to increase survival of bacteria under various conditions, this phenotype indicates a change in bacterial responses that are potentially related to the increased virulence of the flight-grown S. typhimurium.

    S. typhimurium from flight and ground cultures were harvested and immediately used to inoculate rodents on the same day as the STS-115/12A landing. Rodents infected with bacteria from the space cultures displayed a decreased time to death and increased percent mortality at each infection dosage compared with those infected with ground controls. These data indicate increased virulence for space flight S. typhimurium samples. The results of this work were recently published in the Proceedings of the National Academy of Sciences (Wilson, et al., 2007). Data for P. aeruginosa and C. albicans samples are currently being analyzed.

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    Related Web Sites
  • The Biodesign Institute - Arizona State University
  • Article: Space flight shown to alter ability of bacteria to cause disease
  • Ames Research Center - Microbe Hardware
  • The Biodesign Institute Arizona State University

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    Publications

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    Ground Based Results Publications

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    ISS Patent Publications

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    Related Publications
    • Nickerson C A,Ott C M,Wilson J W,Ramamurthy R ,LeBlanc C L,Honer zu Bentrup K ,Hammond T ,Pierson D L,Low-shear modeled microgravity: a global environmental regulatory signal affecting bacterial gene expression, physiology, and pathogenesis Journal of Microbiolological Methods 2003 54 1-11
    • Nickerson C A,Ott C M,Wilson J W,Ramamurthy R ,Pierson D L,Microbial Responses to Microgravity and Other Low-Shear Environments Microbiology and Molecular Biology Reviews 2004 68 345-361
    • Pierson D L,Wilson J ,Ramamurthy R ,Porwollik S ,McClelland M ,Hammond T ,Allen P ,Ott C M,Pierson D L,Nickerson C A,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 13807-11382
    • Wilson J ,Ott C M,Ramamurthy R ,Porwollik S ,McClelland M ,Pierson D L,Nickerson C A,Low-Shear modeled microgravity alters the Salmonella enterica serovar typhimurium stress response in an RpoS-independent manner Applied and Environmental Microbiology 2002 68 5408-5416
    • Nickerson C A,Ott C M,Mister S J,Morrow B J,Burns-Keliher L ,Pierson D L,Microgravity as a Novel Environmental Signal Affecting Salmonella enterica Serovar Typhimurium Virulence Infection and Immunity 2000 68 3147-3152
    • Wilson J W,Schurr M J,LeBlanc C L,Ramamurthy R ,Buchanan K L,Nickerson C A,Mechanisms of bacterial pathogenicity Journal of Postgraduate Medicine 2002 78 216-224

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    Images

    imageImage of Candida albicans.This is one of three microbial pathogens examined for the Microbe investigation. Image courtsey from Arizonia State University.


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    imageImage of gram negative Salmonella typhimurium. This is one of three microbial pathogens examined for the Microbe investigation. Image courtsey from Arizonia State University.


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    Information provided by the investigation team to the ISS Program Scientist's Office.
    If updates are needed to the summary please contact JSC-ISS-Program-Science-Group. For other general questions regarding space station research and technology, please feel free to call our help line at 281-244-6187 or e-mail at JSC-ISS-Payloads-Helpline.
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