Response of selected microorganisms to a simulated martian environment

Abstract

Microorganisms capable of growth at 7 C were enumerated and isolated from soil samples from the manufacture area (Denver, Colorado) and assembly area (Cape Kennedy, Florida) of the Viking spacecraft. Temperature requirements were determined for these isolates, and those growing at 3 C, but not at 32 C were designated as obligate psychrophiles in this investigation. These were identified to major generic groups, and the population density of obligate psychrophiles from the various groups was determined. It was found that soil samples from the manufacture area contained obligate psychrophiles, none of which was sporeformers, which compromised about 15% of the population isolated at 7 C. The samples from Cape Kennedy contained psychrophilic populations which made up about 16% of the population isolated at 7 C, and 5% of these were aerobic sporeformers. Growth responses of the psychrophilic populations in the original soil samples and heat-shocked soil samples in a simulated Martian environment were determined. Evidence is presented to show that none of the populations in the original samples from the manufacture area was capable of growth under the experimental conditions, but populations in 7 of the 11 soil samples from Cape Kennedy did grow under these conditions. Populations in the 3 heat-shocked soil samples from Cape Kennedy were able to grow in the experimental environment..