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Effect of Spaceflight on Microbial Gene Expression and Virulence (Microbe)
03.13.09

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

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

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

    • Payload Developer

    Ames Research Center, Moffett Field, CA

    Sponsoring Agency

    National Aeronautics and Space Administration (NASA)

    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

    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 will utilize 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. 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 will be 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 will be stopped by a crewmember turning the hand crank once more. Upon landing, one third of the samples will be recovered as soon as possible and the live cells will be used immediately for the virulence studies while the remaining stabilized samples will be frozen at minus 80 degrees C. Ground analysis will focus 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 will lead to the development of novel 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).

    Looking at 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
  • 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

    Results Publications

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      Related Publications
      • Wilson JW, Schurr MJ, LeBlanc CL, Ramamurthy R, Buchanan KL, Nickerson CA Mechanisms of bacterial pathogenicity. Journal of Postgraduate Medicine. ;78(918):216-224. 2002
      • Nickerson CA, Ott CM, Mister SJ, Morrow BJ, Burns-Keliher L, Pierson DL. Microgravity as a Novel Environmental Signal Affecting Salmonella enterica Serovar Typhimurium Virulence. Infection and Immunity. ;68(6):3147-3152. 2000
      • Wilson J, Ott CM, Ramamurthy R, Porwollik S, McClelland M, Pierson DL, Nickerson CA. Low-Shear modeled microgravity alters the Salmonella enterica serovar typhimurium stress response in an RpoS-independent manner. Applied and Environmental Microbiology. ;68(11):5408-5416. 2002
      • Wilson J, Ramamurthy R, Porwollik S, McClelland M, Hammond T, Allen P, Ott CM, Pierson DL, Nickerson CA. 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. ;99(21):13807-11382. 2002
      • Nickerson CA, Ott CM, Wilson JW, Ramamurthy R, LeBlanc CL, Honer zu Bentrup K, Hammond T, Pierson DL. Low-shear modeled microgravity: a global environmental regulatory signal affecting bacterial gene expression, physiology, and pathogenesis. Journal of Microbiol Methods. ;54(1):1-11. 2003
      • Nickerson CA, Ott CM, Wilson JW, Ramamurthy R, Pierson DL. Microbial Responses to Microgravity and Other Low-Shear Environments. Microbiology and Molecular Biology Reviews. ;68(2):345-361. 2004

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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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      imageScanning Electron Micrograph (SEM) of gram negative Pseudomonas aeruginosa. This is one of three microbial pathogens examined for the Microbe investigation. Image courtsey from Arizonia State University.
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      imageNASA Image: S115e07274 - Astronaut Heidemarie M. Stefanyshyn-Piper, Mission Specialist holding the Microbe Group Activation Pack containing eight Fluid Processing Apparatuses in the middeck of the Space Shuttle Atlantis during Expedition 13 and STS-115 joint operations.
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      imageThe Group Activation Pack (GAP), left, is a triple-enclosed containment vessel used to house microbiology experiments in microgravity. The Ground-based bioreactor, right, is used in ground studies to simulate microgravity in the laboratory. (Photo courtesy of Arizona State University)
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      imageResearcher Hami Teal, Ph.D. examines hardware for Microbe experiment. Image courtesy of Ames Research Center.
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      imageResearcher Hami Teal, Ph.D. examines and activates the hardware for Microbe experiment. Image courtesy of Ames Research Center.
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      imagePrincipal Investigator Cheryl Nickerson, Ph.D. Image courtesy of the Biodesign Institute, Arizona State University.
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      Information Provided and Updated by the ISS Program Scientist's Office
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