Organic acid production from CO2/H2 and CO/H2 by mixed-culture anaerobes

The gases CO, CO₂, and H₂ were used as substrates in anaerobic fermentations producing organic acids. Various mixed bacterial sources were used, including sewage sludge digester effluent, rabbit feces, and soil. Nonsterile microorganism selection was carried out using CO₂/H₂ and CO/H₂ as the primary carbon and energy sources. Cultures were grown in specially designed, high-pressure (to 70 psig) flasks. Methanogenic bacteria were eliminated from the cultures. Liquid products of the fermentations were acetic through caproic acids, with the even-numbered acids predominating. Carbon balances showed conclusively that acetic acid was formed from carbon contained in the CO or CO₂ feed gas. Measurements made included rates of acid product formation, cell density, and degree of gas utilization. Limited characterization of the microorganisms was also performed. Production of organic acids by mixed culture inocula from CO₂/H₂ or CO/H₂ had not been reported previously. Application of this work is to the production of organic chemicals from synthesis gas (SNG), produced by the gasification of fossil fuels (peat, lignite, and various ranks of coals), biomass (agricultural and forest residues, and various biomass crops grown expressly for energy recovery), and municipal solid waste.     

Influence of lipopolysaccharide and protein in the cell envelope on recipient capacity in conjugation of Salmonella typhimurium.

In crosses of Salmonella typhimurium FfinP301 lac+ to F- strains of S. typhimurium in broth, recipient strains which were rough mutants affected in the outer core region of the lipopolysaccharide gave an average of 1.4 Lac+ transconjugants per donor cell and over 50% of the donor and recipient cells in mating aggregates, whereas smooth recipient strains gave 0.08 Lac+ transconjugants and few cells in mating aggregates. Strains with mutations affecting the inner core of the lipopolysaccharide were usually poor recipients. When cells were mated on Millipore membrane filters, both smooth and rough strains gave ca. 1.0 Lac+ transconjugants per donor cell. Plasmids in Inc groups FI, FII, M, J, and I beta gave more transconjugants with rough than smooth strains, but there were no difference in crosses with plasmids in Inc groups T, L, P, N, and W. Strains with mutations in the ompA gene (deficient in Omp Ap = 33K = II* = conjugation protein) yielded only 0.02 Lac+ transconjugants per donor cell and few cells in mating aggregates. There was no indication of a deficiency of Omp Ap in smooth strains compared with rough strains. Reduced fertility of smooth recipients may occur because the O side chains of the lipopolysaccharide shield the recipient and reduce the frequency of stabilization of mating aggregates. However, gradient-of-transmission experiments indicated that once these mating aggregates are stabilized, they are equally stable in both smooth and rough recipients. Fertility was high in crosses of S. typhimurium Flac+ to Escherichia coli K-12 F- (0.75 Lac+ transconjugants per donor cell; over 50% of the cells in mating aggregates). In crosses of E. coli K-12 Flac+ to S. typhimurium smooth F-, ca. 10(-5) Lac+ transconjugants per donor cell were obtained; in crosses to rough recipient strains, fertility was increased 14-fold, and when the recipient was defective in the SA and LT host restriction systems, fertility was increased in additional 100-fold. Thus, both the lipopolysaccharide and the protein in the cell envelope of S. typhimurium were shown to be important in the recipient function in F-mediated conjugation.     

9-beta-D-Arabinofuranosyl-8-n-butylaminoadenine, a C-8 substituted nucleoside in the anti conformation. Crystallographic and NMR studies

The protein NMR spectrum of 9-beta-D-arabinofuranosyl-8-n-butylaminoadenine shows an unusually low-field 5'-hydroxyl proton resonance, which has been interpreted in terms of an anti glycosidic conformation together with an 05' ... N8 intramolecular hydrogen bond. Confirmatory evidence for this was obtained by an X-ray crystallographic study; in the crystal, the glycosidic angle chi is 52.7 degrees and the sugar pucker is C3' endo-C4' exo.     

Polyamine metabolism in BHK21/C13 cells : Loss of spermidine from cells following transfer to serum-depleted medium

The growth rate of BHK21/C13 cells in culture was slowed down by transferring growing cells to serum-depleted medium Following deprivation of serum, the intracellular concentration of polyamines decreased. The amount of spermidine relative to spermine decreased, and this change was the result of the spermidine content per cell decreasing more than the spermine content. The decrease in cell content of polyamines was accompanied by release of polyamines from the cells into the culture medium. The polyamines released were examined using cells whose polyamines had been labelled by prior incubation of the cells with radioactive putrescine. Almost all of the radioactivity released into the medium was found in spermidine, even though the cells contained most of their radioactivity in spermine. It is suggested that specific release of spermidine may be an important mechanism by which these cells can regulate their intracellular content of polyamines.     

Stable transformation of papaya via microprojectile bombardment

Summary Stable transformation of papaya (Carica papaya L.) has been achieved following DNA delivery via high velocity microprojectiles. Three types of embryogenic tissues, including immature zygotic embryos, freshly explanted hypocotyl sections, and somatic embryos derived from both, were bombarded with tungsten particles carrying chimeric NPTII and GUS genes. All tissue types were cultured prior to and following bombardment on half-strength MS medium supplemented with 10 mg 1^–1 2,4-D, 400 mg 1^–1 glutamine, and 6% sucrose. Upon transfer to 2,4-D-free medium containing 150 mg 1^–1 kanamycin sulfate, ten putative transgenic isolates produced somatic embryos and five regenerated leafy shoots. Leafy shoots were produced six to nine months following bombardment. Tissues from 13 of these isolates were assayed for NPTII activity, and 10 were positive. Six out of 15 isolates assayed for GUS expression were positive. Three isolates were positive for both NPTII and GUS,Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GUS -glucuronidase - X-gluc 5-Br-4-Cl-3-indolyl--D-glucuronic acid - CaMV cauliflower mosaic virus - NOS nopaline synthase - NPTII neomycin phosphotransferase II Journal Series no. 3448 of the Hawaii Institute of Tropical Agriculture and Human Resources     

Deriving phylogenetic trees from the similarity analysis of metabolic pathways

MOTIVATION: Comparative analysis of metabolic pathways in different genomes can give insights into the understanding of evolutionary and organizational relationships among species. This type of analysis allows one to measure the evolution of complete processes (with different functional roles) rather than the individual elements of a conventional analysis. We present a new technique for the phylogenetic analysis of metabolic pathways based on the topology of the underlying graphs. A distance measure between graphs is defined using the similarity between nodes of the graphs and the structural relationship between them. This distance measure is applied to the enzyme-enzyme relational graphs derived from metabolic pathways. Using this approach, pathways and group of pathways of different organisms are compared to each other and the resulting distance matrix is used to obtain a phylogenetic tree. RESULTS: We apply the method to the Citric Acid Cycle and the Glycolysis pathways of different groups of organisms, as well as to the Carbohydrate metabolic networks. Phylogenetic trees obtained from the experiments were close to existing phylogenies and revealed interesting relationships among organisms.     

Molecular Mechanisms of Ischemia–Reperfusion Injury in Brain: Pivotal Role of the Mitochondrial Membrane Potential in Reactive Oxygen Species Generation

Stroke and circulatory arrest cause interferences in blood flow to the brain that result in considerable tissue damage. The primary method to reduce or prevent neurologic damage to patients suffering from brain ischemia is prompt restoration of blood flow to the ischemic tissue. However, paradoxically, restoration of blood flow causes additional damage and exacerbates neurocognitive deficits among patients who suffer a brain ischemic event. Mitochondria play a critical role in reperfusion injury by producing excessive reactive oxygen species (ROS) thereby damaging cellular components, and initiating cell death. In this review, we summarize our current understanding of the mechanisms of mitochondrial ROS generation during reperfusion, and specifically, the role the mitochondrial membrane potential plays in the pathology of cerebral ischemia/reperfusion. Additionally, we propose a temporal model of ROS generation in which posttranslational modifications of key oxidative phosphorylation (OxPhos) proteins caused by ischemia induce a hyperactive state upon reintroduction of oxygen. Hyperactive OxPhos generates high mitochondrial membrane potentials, a condition known to generate excessive ROS. Such a state would lead to a “burst” of ROS upon reperfusion, thereby causing structural and functional damage to the mitochondria and inducing cell death signaling that eventually culminate in tissue damage. Finally, we propose that strategies aimed at modulating this maladaptive hyperpolarization of the mitochondrial membrane potential may be a novel therapeutic intervention and present specific studies demonstrating the cytoprotective effect of this treatment modality.     

The roles of integration in molecular systems biology

A common way to think about scientific practice involves classifying it as hypothesis- or data-driven. We argue that although such distinctions might illuminate scientific practice very generally, they are not sufficient to understand the day-to-day dynamics of scientific activity and the development of programmes of research. One aspect of everyday scientific practice that is beginning to gain more attention is integration. This paper outlines what is meant by this term and how it has been discussed from scientific and philosophical points of view. We focus on methodological, data and explanatory integration, and show how they are connected. Then, using some examples from molecular systems biology, we will show how integration works in a range of inquiries to generate surprising insights and even new fields of research. From these examples we try to gain a broader perspective on integration in relation to the contexts of inquiry in which it is implemented. In today's environment of data-intensive large-scale science, integration has become both a practical and normative requirement with corresponding implications for meta-methodological accounts of scientific practice. We conclude with a discussion of why an understanding of integration and its dynamics is useful for philosophy of science and scientific practice in general.