For loading, a single clone of each bacteria are grown overnight, and the resulting cultures are diluted to a final concentration of 120 cells/ml for S. typhimurium and 187 cells/ml for E. coli. Cultures are maintained in suspension in spinner flasks over ice throughout loading into experiment packages, in order to impose a two-hour lag time prior to the start of cell growth. S. typhimurium cultures are loaded into the top series of chambers, and E. coli are loaded into the chambers on the lower side of the package. Samples are made at the start and completion of loading procedures to confirm that no growth has occurred. Packages are kept on ice until mated with the spacecraft. LiF dosimeters are included in each package.