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.Principal Investigator(s)
Ames Research Center, Moffett Field, CA, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)ISS Expedition Duration
March 2011 - September 2011
27/28Previous ISS Missions
Increment 27/28 is the first planned mission for the Microbe-4 investigation.
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.Earth Applications
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.
Late Load L- 28 hrs, Early Recovery R+ 6 hours.Operational Protocols
This experiment is still in the Phase A, experiment definition phase, therefore the operational protocols for this experiment have not been finalized.