ALBERT

Notes: Summary The results of the Viking Biology experiments are best explained by non-biological phenomena: The interaction of the reagents with the materials comprising the regolith. Conditions of water activity, temperature, availability of carbon sources and others in most regions of the planet are too extreme for survival and growth of any known Earth microorganisms. Although the possibility persists that some very unusual form of life is somewhere on that planet the evidence is best interpreted as negative. Even though there is no evidence for current life on Mars, whether or not life ever originated there is not known.

Notes: Summary The regulation of GAL1 RNA and enzyme synthesis has been investigated in Saccharomyces cerevisiae. We have shown that the induction of GAL10 and GAL1 RNAs is coordinate. GAL1 RNA transcripts appear within 4.5 to 6 min and galactokinase synthesis within 6 to 9 min. Steady-state RNA levels were reached within 50 min and the steady-state rate of galactokinase enzyme synthesis within 40–50 min. From these kinetic studies, the initial induction of GAL1 enzyme activity is apparently under transcriptional control. In addition, during early induction, two galactokinase enzyme activities were detected; a major stable form and a minor unstable form.

Notes: Abstract A central purpose of Viking was to search for evidence that life exists on Mars or may have existed in the past. The missions carried three biology experiments the prime purpose of which was to seek for existing microbial life. In addition the results of a number of the other experiments have biological implications: (1) The elemental analyses of the atmosphere and the regolith showed or implied that the elements generally considered essential to terrestrial biology are present. (2) But unexpectedly, no organic compounds were detected in Martian samples by an instrument that easily detected organic materials in the most barren of terrestrial soils. (3) Liquid water is believed to be an absolute requisite for life. Viking obtained direct evidence for the presence of water vapor and water ice, and it obtained strong inferential evidence for the existence of large amounts of subsurface permafrost now and in the Martain past. However it obtained no evidence for the current existence of liquid water possessing the high chemical potential required for at least terrestrial life, a result that is consistent with the known pressure-temperature relations on the planet's surface. On the other hand, the mission did obtain strong indications from both atmospheric analyses and orbital photographs that large quantities of liquid water flowed episodically on the Martian surface 0.5 to 2.5 G years ago. The three biology experiments produced clear evidence of chemical reactivity in soil samples, but it is becoming increasingly clear that the chemical reactions were nonbiological in origin. The unexpected release of oxygen by soil moistened with water vapor in the Gas Exchange experiment together with the negative findings of the organic analysis experiment lead to the conclusion that the surface contains powerful oxidants. This conclusion is consistent with models of the atmosphere. The oxidants appear also to have been responsible for the decarboxylation of the organic nutrients that were introduced in the Label Release experiment. The major results of the GEX and LR experiments have been simulated at least qualitatively on Earth. The third, Pyrolytic Release, experiment obtained evidence for organic synthesis by soil samples. Although the mechanism of the synthesis is obscure, the thermal stability of the reaction makes a biological explanation most unlikely. Furthermore, the response of soil samples in all three experiments to the addition of water is not consistent with a biological interpretation. The conditions now known to exist at and below the Martian surface are such that no known terrestrial organism could grow and function. Although the evidence does not absolutely rule out the existence of favourable oases, it renders their existence extremely unlikely. The limiting conditions for the functioning of terrestrial organisms are not the limits for conceivable life elsewhere, and accordingly one cannot exclude the possibility that indigenous life forms may currently exist somewhere on Mars or may have existed sometime in the past. Nevertheless, the available information about the present Martian environment puts severe constraints and presents formidable challenges to any putative Martian organisms. The Martian environment in the past, on the other hand, appears to have been considerably less hostile biologically, and it might possibly have permitted the origin and transient establishment of a biota.

Notes: Summary Studies were undertaken to elucidate the role of the GAL4 locus in regulating the galactose catabolic enzymes in Saccharomyces cerevisiae. The GAL4 locus has been proposed to have a regulatory function since GAL4 mutants are pleiotropic, lacking epimerase, galactokinase, transferase and galactose permease activities. This pleiotropic effect could be explained if the GAL4 gene codes for a peptide required for above enzyme activities. To study if the GAL4 gene codes for a structural component of the above enzymes, a temperature sensitive mutation mapping close to or within the GAL4 gene (gal4-1ts) was isolated. The results suggest that the GAL4 locus does not code for a polypeptide common to the transferase, epimerase, galactokinase, and permease enzymes since these enzymes extracted from the gal4-1ts mutant did not differ qualitatively in thermolability and temperature optima from those of the wild-type. It was found that in the gal4-1ts mutant the synthesis of the epimerase is temperature sensitive and that the GAL4 gene product does not have any effect on the in vivo stability of epimerase.

Notes: Summary Various amino acid insertions have been introduced into the proximal portion of the signal sequence of secreted yeast invertase. The altered invertase genes have been reintroduced into yeast and monitored for their ability to direct synthesis of secreted invertase in vivo. The insertions should alter the signal polypeptide local secondary structure as predicted by the Chou and Fasman rules (1978). Secretion of these altered invertase polypeptides is not blocked by the amino acid insertions.

Notes: Abstract Several phosphomonoesterases and diesterases with various pH optima have been observed inAcinetobacter lwofi JW11. The osmotic shock fluids contained only those with an alkaline pH optimum. The synthesis of these phosphatases was regulated by external Pi concentrations. The shock fluids were fractionated by chromatography, yielding three fractions, two of which had hydrophobic properties. One of these contained an alkaline phosphatase that specifically required Ca2+ for activity. The diesterases required various divalent cations for their function. Mutants that lack phosphomonoesterase or both phosphomonoesterase and phosphodiesterase activities were isolated.

Notes: Abstract The transport of inorganic phosphate has been studied inAcinetobacter lwoffi JW11. During growth on excess phosphate, only one transport system was present, with an apparent Km of 1.4 μM. When cells were starved for phosphate, a second uptake system with an apparent Km of 110 nM was also synthesized. The two transport systems could be distinguished by differing sensitivities to the phosphate analogs arsenate and 2-aminoethylphosphonate. Both systems were inhibited by carbonylcyanidem-chlorophenylhydrazone, and to a lesser extent by Na azide. The high-affinity transport system was inactivated by osmotic shock treatment and by spheroplast formation. Preliminary evidence for a phosphate-binding protein in the osmotic shock fluid is presented. The isolation of a mutant constitutive for the high-affinity transport system is described.