Genotypic and Phenotypic Changes in Yeast Related to Selective Growth Pressures Unique to Microgravity (Micro-4) - 07.14.16
The Genotypic and Phenotypic Changes in Yeast Related to Selective Growth Pressures Unique to Microgravity (Micro-4) study investigates how yeast cells adapt to the unique aspects of the space environment by using the yeast deletion series; a collection of yeast strains where every gene has been individually knocked out. In this manner, the selective growth of every strain in the yeast deletion series can be analyzed. Science Results for Everyone
Information Pending Experiment Details
Timothy G. Hammond, M.B.B.S., Durham Veterans' Affairs Medical Center, Durham, NC, United States
Michael Costa, University Toronto of Canada
Corey Nislow, seqWell Inc., Beverly, MA, United States
Louis S. Stodieck, Ph.D., University of Colorado, BioServe Space Technologies, Boulder, CO, United States
NASA Ames Research Center, Moffett Field, CA, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2011 - September 2011
Increment 27/28 is the first planned mission for the Microbe-4 investigation.
- The goal of Genotypic and Phenotypic Changes in Yeast Related to Selective Growth Pressures Unique to Microgravity (Micro-4) is to understand the different responses and physical effects of microgravity on yeast cells by examining which specific deletion strains best survive.
- Direct assessment of selective pressures on cell populations through generations using the yeast deletion series is a critical experiment to directly address risks to biological integrity and life-based support systems for long-term occupation of space.
- Results from this study allow researchers to obtain a global perspective on all the genes that play a role in survival under microgravity conditions.
The goal of the Micro-4 experiment is to investigate how cells adapt to the unique aspects of the space environment, using the model eukaryotic (having cells that contain complex structures enclosed in membranes) organism, Saccharomyces cerevisiae (S. cerevisiae) (a budding yeast useful in baking). Direct assessment of selective pressures on cell populations through generations has become possible due to the recent availability of the yeast deletion series. This powerful reagent consists of a collection of molecularly engineered isogenic (having the same genetic makeup) yeast strains that differ only in a single gene locus (i.e. only one of a possible 6000 genes is deleted) and each deleted gene has been replaced with a selectable marker and a unique identifying “barcode”. The deletions mutant can be grown under a selective pressure in an arrayed format on solid agar media in petri dishes and cell growth is assessed by measuring yeast colony size. Alternatively, the mutant strain collection can grow in a pooled format, DNA extracted, and the barcodes amplified by PCR (polymerase chain reaction - enables researchers to produce millions of copies of a specific DNA sequence). The resulting product is annealed (when DNA or RNA pairs by hydrogen bonds) to a gene microarray chip comprising spots for the complementary sequence of each barcode. In this manner, the selective growth of every strain in the yeast deletion series can be assayed in a single tube, enabling a genomic approach to phenotypic analyses.
Direct assessment of selective pressures on cell populations through generations using the yeast deletion series is a critical experiment to directly address risks to biological integrity and life-based support systems for long-term occupation in space. Results from this study allow researchers to gain a global perspective to the genes that play a role in survival, in regards to microgravity conditions, and will allow for a more thorough understanding of the effects of microgravity on a model organism. The expectation is that what is observed in yeast is likely to have a comparable effect in mammalian cells. This is supported by the observation that regulatory mechanisms are largely conserved between yeast and mammalian cells.
Fundamental Space Biology (FSB) uses the space environment to probe the fundamental nature of life on Earth in order to enhance the understanding of how life responds to physical forces on Earth and in space.
Operational Requirements and Protocols
Late Load L- 28 hrs, Early Recovery R+ 6 hours.
This experiment is still in the Phase A, experiment definition phase, therefore the operational protocols for this experiment have not been finalized.
Decadal Survey Recommendations
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Spaceflight has serious effects on human biological systems, and while yeast cannot completely reflect the complexities of a mammalian tissues, the high degree of common genes between yeast and human (~70%) makes them ideal for studying the mechanism of many cellular responses to space stress. Biological responses of yeast strains during spaceflight can be quantified and compared to well-established databases of ground-based stressors and the comparisons can reveal features that are unique to microgravity. Modified yeast strains carrying a deletion of a gene required for survival in the presence of the stressor grow more slowly, and since all genes required for growth can be readily identified in a single experiment, the genes and associated pathways affected by spaceflight can be revealed. Chemo-genetic analysis of spaceflight samples shows DNA and RNA damage similar to the effects of DNA-damaging agents, such as radiation exposure, and changes in redox state. Furthermore, impacts on DNA repair and replication, response to pH signaling, control of gene expression, and mitochondrial function were observed. The results from these experiments suggest that spaceflight has subtle but significant effects on core cellular processes including growth control via RNA and ribosomal production, metabolism, modification and decay pathways. These pathways, which are required for survival in spaceflight, can guide future experiments in two fundamental ways: first by providing environmental modifications that can eliminate or reduce stress to these pathways, and secondly, by identifying drug to help control harmful cell growth in the case of proliferative diseases. The experiments represent a proof of principle for conducting full genome environmental screens in spaceflight using robust automated hardware in the space of a small suitcase. The performance of this platform is significant for spaceflight studies and promises to enable terrestrial experiments in extreme environments, as well, that may be applied to microbial bioprocessing for manufacturing, alternative fuel development and basic research.^ back to top
Nislow C, Lee AY, Allen PL, Giaever G, Smith A, Gebbia M, Stodieck LS, Hammond JS, Birdsall HH, Hammond TG. Genes required for survival in microgravity revealed by genome-wide yeast deletion collections cultured during spaceflight. BioMed Research International. 2015; 2015(976458): 10 pp. DOI: 10.1155/2015/976458.
Ground Based Results Publications
NASA Science News - Space: A bad influence on microbes?
Enhanced microscopic image of the yeast fungi Saccharomyces cerevisiae.
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