Relationship Between Protein and Ribonucleic Acid Synthesis During Outgrowth of Spores of \u3ci\u3eBacillus cereus\u3c/i\u3e

The rate of protein and ribonucleic acid (RNA) synthesis was examined during the outgrowth of spores of Bacillus cereus T in a chemically defined medium. RNA synthesis started 2.5 min after the initiation of germination, and protein synthesis after 4 min. Addition of a complete amino acid supplement and uracil supported high rates of RNA and protein synthesis throughout outgrowth. To determine the relationship between the rate of protein (k) and RNA synthesis, the kinetics of formation of various classes of RNA were followed during outgrowth. Ribosomal RNA (rRNA) comprised a relatively constant fraction of the total RNA throughout outgrowth (71 to 78%). The classes of RNA synthesized during this period were determined by germinating spores in radioactive uracil and then at intervals following their stability to actinomycin D. Initially, labile RNA comprised the largest fraction of newly formed RNA (ΔRNA), and this proportion decreased during outgrowth. The ratio of k/rRNA or k/Δ stable RNA varied considerably during outgrowth, whereas the ratio of k/labile RNA remained constant. The data suggest that the rate of protein synthesis is not rigidly coupled to either total or newly synthesized rRNA (ribosomes) during the early stages of outgrowth

The Viking Mission: Implications for Life on Mars

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