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Saccharomyces Cerevisiae Uses Gas Producing Anaerobic Metabolic Pathways During Space Flight. Timothy G Hammond^1,2, , Cheryl A Nickerson³, Jake Freeman⁴, Louis S Stodieck⁴, and Patricia L Allen¹. ¹Department of Medicine, Tulane University School of Medicine, & VAMC, New Orleans, LA, ³Center for Infectious Diseases and Vaccinology, Arizona State Univ., Tempe AZ, ; and ⁴BioServe Space Technologies, University of Colorado, Boulder, CO.

   As part of a large-scale effort to examine the function of all yeast genes, a consortium of investigators created a series of heterozygous and homozygous diploid strains, each containing a deletion of a single gene allele. A selectable marker that carries adjacent gene specific oligonucleotide sequences replaces each gene.  These sequences serve as an identifier of the locus essentially acting as a barcode.  The individual strains can then pooled so that all are represented in equimolar amounts, and grown en mass.  The result of this genomic approach to a selective growth condition has been coined "fitness profiling". We dried down multiple identical aliquots of these heterozygous and homozygous diploid strain pools on filters, and loaded them into 3 compartment glass tubes (Fluid Processing Apparatus - FPA).  The first compartment in each tube contained the dried yeast with growth media and fixative loaded in the other two compartments, respectively. Eight FPAs were loaded into hand cranked containers (Group Activation Packs –GAPs) for simultaneous activation. Two GAPs were held for ground based activation in the investigators lab at Tulane in New Orleans, two shipped to Moscow, and two more launched to the International Space Station (Mission 13P) and grown for 72 hours. All samples grew robustly. However, there were dramatic differences in gas production as the homozygous yeast pool flight samples produced 2.73+0.39 ml of gas (mean + standard error, n=6), while both the Russian controls (0.16+0.07) and the Tulane growth controls (0+0.02) produced significantly less gas (p<0.01, ANOVA and Tukey’s post hoc test). The pattern in the heterozygous yeast pool was similar but less marked. This demonstrates a near complete switch from anaerobic carbon dioxide producing pathways in flight, to aerobic carbon dioxide free metabolic pathways on the ground.