An understanding of the basic cellular mechanisms organisms use to cope with extreme environments is important as we search for life in other parts of the universe and seek to adapt terrestrial life beyond earth. Radiation Monitoring Devices, Inc. proposes to build an automated, high-throughput instrument to measure changes in protein expression levels in single living cells during passage in a space environment. Commercial libraries of clones expressing GFP (green fluorescent proteins) fused to individual yeast proteins are available for the entire yeast proteome. We will test the feasibility of using fluorescence measurements of these chimeric fusion proteins as an indicator of changes in the expression levels of the endogenous proteins upon exposure to radiation. Our instrument consists of a continuous, multi-well, suspension culture bioreactor that provides yeast clones that are sampled in a microfluidic flow cytometer. Light scattering and fluorescent signals from the yeast particles under flow will activate an in-line cell sorter to collect cells of interest for follow-up analysis. Since the instrument is self-contained, has low power consumption and a small footprint, and uses fluidic based cell separation, it will be suitable for collecting single cell protein expression information in a space laboratory.