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Previous investigators have reported that the microbiological population of the glacier free valleys of southern Victorialand, Antarctica, is sparse, and that from about 10% of the soil samples examined no micro-organisms could be cultivated. Since these areas are assumed to be more favorable to the growth of terrestrial organisms than any Martian environment, the previous authors concluded that the probability of terrestrial organisms growing on Mars would therefore be so small that sterilization standards could be relaxed by many orders of magnitude. The unsuitability of the Antarctic environment to the multiplication of terrestrial micro-organisms was ascribed by them to limiting amounts of water. We have carried out a survey of a variety of environments in the dry valleys, ranging from mountain crests to valley floors. The main purpose of our investigation was the determination of active microbial multiplication in the soil. A series of techniques was employed which permitted the detection of bacterial growth in situ. All evidence points to an active growth of micro-organisms in the Antarctic soil in all locations which we examined. The measurements were supported by electron micrographs of soil films which showed colonial growth covering soil particles. These findings suggest that Antarctica does not serve as a useful model for the Martian environment in evaluating quarantine standards.

Nicotinamide adenine dinucleotide phosphate (reduced form) is formed more rapidly after the addition of thiosulfate to suspensions of intact Thiobacillus neapolitanus in the absence of CO(2) than nicotinamide adenine dinucleotide (reduced form). Measurement of acid-stable metabolites shows this phenomenon to be the result of rapid reoxidation of nicotinamide adenine dinucleotide (reduced form) by 3-phosphoglyceric acid and other oxidized intermediates, which are converted to triose and hexose phosphates, and that, in reality, the rate of nicotinamide adenine dinucleotide (oxidized form) reduction exceeds that of nicotinamide adenine dinucleotide phosphate (oxidized form) by approximately 4.5-fold. The overall rate of pyridine nucleotide reduction by thiosulfate (264 nmol per min per mg of protein) is in excess of that rate needed to sustain growth. Pyridine nucleotide reduction, adenosine triphosphate synthesis, and carbohydrate synthesis are prevented by the uncoupler m-Cl-Carbonylcyanide phenylhydrazone. Sodium amytal inhibits pyridine nucleotide reduction and carbohydrate synthesis are prevented by the uncoupler m-Cl-carbonylcyanide observations are reproduced when sulfide serves as the substrate. The rate of pyridine nucleotide anaerobic reduction with endogenous substrates or thiosulfate is less than 1% of the aerobic rate with thiosulfate. We conclude that the principal, if not the only, pathway of pyridine nucleotide reduction proceeds through an energy-dependent and amytal-sensitive step when either thiosulfate or sulfide is used as the substrate.