Binding of aminoacyl-tRNA to rat liver ribosomal proteins

Rat liver ribosome treatment with ethanol and 1 M NH₄Cl releases some 31–33 ribosomal proteins. This split protein fraction binds Phe-tRNA, Ac-Phe-tRNA, Met-tRNA_M and f-Met-tRNA_F in the absence of K⁺ and Mg⁺⁺ ions. When the split protein fraction is passed through Sephadex G-100 only six proteins are retained in the column: S10, S14, S15, S19, L35, and L36. The aminoacyl-tRNA binding activity of this protein fraction retained in the Sephadex G-100 column is similar to that of the total split protein fraction, suggesting that the above six proteins, or only some of them, are involved in the binding reaction.     

Potential Pathogens in the Environment: Cultural Reactions and Nucleic Acid Studies on Klebsiella pneumoniae from Clinical and Environmental Sources

The phenotypic and nucleic acid properties of Klebsiella pneumoniae have been studied on cultures obtained from six different habitats (humans, vegetables, seeds, trees, rivers, and pulp mills). The 19 cultural reactions of 107 isolates varied significantly only in tryptophanase activity and dulcitol fermentation. The percentage of guanine plus cytosine base composition of 41 isolates varied from 53.9 to 59.2%. The range of percentage of guanine plus cytosine base composition for environmental klebsiellas was broader than that for the cultures of human origin. The range of deoxyribonucleic acid relative reassociation (homology) to the human K. pneumoniae reference strain extended from 5% to 100% and the chromosome molecular weights ranged from 2,200 × 10⁶ to 3,000 × 10⁶. The species of K. pneumoniae is thus molecularly more heterogeneous than previously thought and most isolates of human, pulp mill, and river origin are genetically indistinguishable. The presence of K. pneumoniae therefore represents a deterioration of the microbiological quality of the environment and should be considered of public health significance. At the present time the health significance of the molecularly more divergent strains, primarily of vegetable and seed origin, their relationship to klebsiellas of human origin, or to other genera of the Enterobacteriaceae is unclear.     

Application of the Deoxyribonucleic Acid/Ribonucleic Acid Hybridization Technique in Bdellovibrio as a Model for Studying Ribonucleic Acid Turnover in Host-Parasite Systems

The kinetics of host ribonucleic acid (RNA) degradation and its resynthesis into Bdellovibrio-specific polyribonucleotides has been studied. The kinetics of RNA turnover was followed during a one-step synchronous growth cycle of Bdellovibrio growing within ³²PO₄-labeled Escherichia coli host cells. The species of labeled RNA present at any given time was ascertained through the specificity of the deoxyribonucleic acid (DNA)/RNA hybridization technique. At nearsaturating levels of RNA and at zero time, 7% of the host DNA sequences and only 0.04% of the Bdellovibrio DNA became hybridized with ³²P-labeled host cell RNA (greater than 99% host specific). At the end of the burst, 98% of the labeled RNA sequences were specific for Bdellovibrio DNA. About 74% of the initial labeled host cell RNA became turned over into Bdellovibrio-specific sequences. We provide data indicating that host cell ribosomal RNA is assimilated by Bdellovibrio. Degradation of host cell RNA occurs in a gradual fashion over most of the Bdellovibrio developmental growth cycle. This application of the DNA/RNA hybridization technique and its general concept should be of value in elucidating the kinetics of nucleic acid turnover in other types of host-parasite systems.     

Voltage-dependent conductance induced by hemocyanin in black lipid films

When hemocyanin is added to a black lipid film, the conductance increases in discrete steps. For negative potentials the single step conductance is constant, but for positive potentials the step conductance appears to decrease as the potential increases. At high positive potentials the conductance fluctuates between several levels. These data suggest that, in lipid membranes, hemocyanin conducts ions through discrete channels. The voltage-dependent conductance observed at high levels of conductance seems to be a consequence of the properties of the conductance of the single channel.     

Truth in wine yeast

Evolutionary history and early association with anthropogenic environments have made Saccharomyces cerevisiae the quintessential wine yeast. This species typically dominates any spontaneous wine fermentation and, until recently, virtually all commercially available wine starters belonged to this species. The Crabtree effect, and the ability to grow under fully anaerobic conditions, contribute decisively to their dominance in this environment. But not all strains of Saccharomyces cerevisiae are equally suitable as starter cultures. In this article, we review the physiological and genetic characteristics of S. cerevisiae wine strains, as well as the biotic and abiotic factors that have shaped them through evolution. Limited genetic diversity of this group of yeasts could be a constraint to solving the new challenges of oenology. However, research in this field has for many years been providing tools to increase this diversity, from genetic engineering and classical genetic tools to the inclusion of other yeast species in the catalogues of wine yeasts. On occasion, these less conventional species may contribute to the generation of interspecific hybrids with S. cerevisiae. Thus, our knowledge about wine strains of S. cerevisiae and other wine yeasts is constantly expanding. Over the last decades, wine yeast research has been a pillar for the modernisation of oenology, and we can be confident that yeast biotechnology will keep contributing to solving any challenges, such as climate change, that we may face in the future.     

Human axillary secretions influence women''s menstrual cycles: The role of donor extract of females

Menstrual synchrony in human females has previously been demonstrated among women attending a predominantly female university as well as among women attending coeducational universities. In each of these studies, women who spent the most time together were most likely to show the menstrual synchrony. In this experiment, the possibility that substances in axillary secretions might mediate this effect was tested using a prospective, double-blind research design and a combined axillary extract from a group of female donors. Female subjects who reported themselves to have normal (29.5 +/- 3 day) cycles were exposed to the axillary extracts or blank/ethanol for 10 to 13 weeks. Recipients of the axillary extracts showed a significant reduction in "days' difference in menses onset" relative to the donor cycle, no change was evident for recipients of blank/ethanol. These results demonstrate that constituents from the axillary region of donor females can shift the time of menstrual onset of another group to conform with the donors' cycle and that this effect can occur even in the absence of social contact.     

A new model for the anaerobic fermentation of glycerol in enteric bacteria: trunk and auxiliary pathways in Escherichia coli

Anaerobic fermentation of glycerol in the Enterobacteriaceae family has long been considered a unique property of species that synthesize 1,3-propanediol (1,3-PDO). However, we have discovered that Escherichia coli can ferment glycerol in a 1,3-PDO-independent manner. We identified 1,2-propanediol (1,2-PDO) as a fermentation product and established the pathway that mediates its synthesis as well as its role in the metabolism of glycerol. We also showed that the trunk pathway responsible for the conversion of glycerol into glycolytic intermediates is composed of two enzymes: a type II glycerol dehydrogenase (glyDH-II) and a dihydroxyacetone kinase (DHAK), the former of previously unknown physiological role. Based on our findings, we propose a new model for glycerol fermentation in enteric bacteria in which: (i) the production of 1,2-PDO provides a means to consume reducing equivalents generated in the synthesis of cell mass, thus facilitating redox balance, and (ii) the conversion of glycerol to ethanol, through a redox-balanced pathway, fulfills energy requirements by generating ATP via substrate-level phosphorylation. The activity of the formate hydrogen-lyase and F(0)F(1)-ATPase systems were also found to facilitate the fermentative metabolism of glycerol, and along with the ethanol and 1,2-PDO pathways, were considered auxiliary or enabling. We demonstrated that glycerol fermentation in E. coli was not previously observed due to the use of medium formulations and culture conditions that impair the aforementioned pathways. These include high concentrations of potassium and phosphate, low concentrations of glycerol, alkaline pH, and closed cultivation systems that promote the accumulation of hydrogen gas.     

GMF-Knockout Mice are Unable to Induce Brain-Derived Neurotrophic Factor after Exercise

We earlier reported that overexpression of glia maturation factor (GMF) in cultured astrocytes enhances the production of brain-derived neurotrophic factor (BDNF). The current study was conducted to find out whether BDNF production is impaired in animals devoid of GMF. To this end GMF-knockout (KO) mice were subjected to exercise and the neurotrophin mRNAs were determined by real-time RT-PCR. Compared to wild-type (WT) mice, there is a decrease in exercise-induced BDNF in the KO mice. The observation was correlated with the finding that, in WT mice, exercise increases GMF expression. The results are consistent with the hypothesis that GMF is necessary for exercise-induction of BDNF, and that GMF may promote neuroprotection through BDNF production.     

Metabolic analysis of the synthesis of high levels of intracellular human SOD in Saccharomyces cerevisiae rhSOD 2060 411 SGA122

The synthesis of human superoxide dismutase (SOD) in batch cultures of a Saccharomyces cerevisiae strain using a glucose-limited minimal medium was studied through metabolic flux analysis. A stoichiometric model was built, which included 78 reactions, according to metabolic pathways operative in these strains during respirofermentative and oxidative metabolism. It allowed calculation of the distribution of metabolic fluxes during diauxic growth on glucose and ethanol. Fermentation profiles and metabolic fluxes were analyzed at different phases of diauxic growth for the recombinant strain (P+) and for its wild type (P-). The synthesis of SOD by the strain P+ resulted in a decrease in specific growth rate of 34 and 54% (growth on glucose and ethanol respectively) in comparison to the wild type. Both strains exhibited similar flux of glucose consumption and ethanol synthesis but important differences in carbon distribution with biomass/substrate yields and ATP production 50% higher in P-. A higher contribution of fermentative metabolism, with 64% of the energy produced at the phosphorylation level, was observed during SOD production. The flux of precursors to amino acids and nucleotides was higher in the recombinant strain, in agreement with the higher total RNA and protein levels. Lower specific growth rates in strain P+ appear to be related to the decrease in the rate of synthesis of nonrecombinant protein, as well as a decrease in the activities of the pentose phosphate (PP) pathway and TCA cycle. A very different way of entry into the stationary phase was observed for each strain: in the wild-type strain most metabolic fluxes decreased and fluxes related to energy reserve synthesis increased, while in the P+ strain the flux of 22 reactions (including PP pathway and amino acids biosynthesis) related to SOD production increased their fluxes. Changes in SOD production rates at different physiological states appear to be related to the differences in building blocks availability between respirofermentative and oxidative metabolism. Using the present expression system, ideal conditions for SOD synthesis are represented by either active growth during respirofermentative metabolism or transition from a growing to a nongrowing state. An increase in SOD flux could be achieved using an expression system nonassociated to growth and potentially eliminating part of the metabolic burden.