Effects of Microgravity on Microbial Physiology

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Microorganisms are capable of quickly adapting to changes in their environment. Metabolic pathways adjust to new environmental conditions to optimize growth and ensure survival. Environmental adaptation is a key tool used in microbial research to investigate the basic physiology of microbial species. Temperature, pH, and growth media constituent manipulation are classic examples of environmental parameter control schemes used to induce observable metabolic changes. </p>
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While classic induced physiology adaptation has been studied extensively, the effects of gravity on microbial physiology remain essentially unknown. Prior space flight research indicates that exposure to microgravity can lead to increased growth rates and increased resistance to antimicrobial agents. However, the limited data and conflicting results of this body of work demand that a well-controlled, prolific methodology be adapted for microbial space flight research. </p>
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The screening phase of the project will investigate the growth, substrate utilization characteristics, and reaction to antimicrobial agents of twelve microbial strains including bacteria and yeasts. These microbes will be analyzed simultaneously on-orbit and on the ground using an automated microbial analysis technology, the Vitek System manufactured by bioMerieux Vitek, Inc. Microbial growth patterns will be measured in standard Vitek identification and antibiotic susceptibility test cards. A physiological profile consisting of observed growth rates, substrate utilization characteristics, and antimicrobial susceptibilities will be obtained for each microbial strain. Physiological profiles from the terrestrial and on-orbit microbial analyses will be compared to determine statistically significant differences in behavior. </p>
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In the second phases of the project, Vitek test cards containing unique media formulations and/or antimicrobial agents will be developed to further investigate each of the specific metabolic differences identified in the screening phase. These test cards will be analyzed in subsequent shuttle flights to elucidate the cellular mechanisms responsible for the observed metabolic anomalies. </p>
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This study will provide a basic understanding of the effects of microgravity on microbial physiology. In addition, the antimicrobial physiological profile data will aid in the development of effective therapeutic treatment for controlling on-orbit infectious disease. </p>
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Adaptation of the Vitek instrument for space flight will provide the first ever on-orbit comprehensive microbial identification capability, an invaluable capability for clinical and environmental microbiology on future long-duration space missions. </p>
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Progress in FY00 has focused on flight preparation. Safety reviews and functional verification testing were completed. Flight documentation including Interface Control Documents, Flight Procedures, and Ground Support Requirements were submitted for approval. Several anticipated hardware development issues were addressed to improve the reliability of the flight hardware. Data acquisition was moved to an external flight support computer. An internal temperature control shutoff feature was modified to handle anticipated increased ambient temperatures on the SpaceHab module. Circulation fan power was routed through an internal power converter to prevent an overvoltage condition. Analytical test card manipulation mechanisms were improved structurally to help prevent interruption of experiment operations. </p>
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The MPFE is aimed at identifying gravity-dependent physiological processes by comparing the growth and metabolism of a broad range of microorganisms. </p>