Ammonium and urea as nitrogen sources for bromeliads

Epiphytic bromeliads have no contact with the pedosphere, so they need to draw their nutrients from the atmosphere as well as from the host tree and animal debris. Terrestrial bromeliads, like Ananas comosus, generally depend on the soil as their main nutrient source. The aim of this study was to investigate and compare some aspects of the nitrogen metabolism of two bromeliads with different growth habits: Ananas comosus, a terrestrial bromeliad, and Vriesea gigantea, an epiphytic tank bromeliad. Nitrogen-starved plants were grown in vitro for 3, 7, 15, 30, and 60 days, either with 5 mmol L⁻¹ ammonium [(NH₄)₂SO₄] or urea as the sole nitrogen source. When NH₄⁺ was supplied to the plants, it stimulated a faster increase of chlorophyll content in A. comosus than in V. gigantea. In the presence of urea, after 15 days of the plants in culture, there was a significant increase in tissue free-NH₄⁺ and total amino acids for V. gigantea only. V. gigantea presented a higher level of total free amino acids than A. comosus when nitrogen was supplied to the plants. Asparagine was the main amino acid accumulated in both bromeliads when plants were transferred to the medium with nitrogen. When the ratio of the main individual free amino acids between the bromeliads grown in NH₄⁺ and urea was compared, values such as 7.2 for asparagine, 5.3 for glutamate, and 1.8 for aspartate in A. comosus, and values such as 2.3 for asparagine, 1.1 for glutamate and 0.7 for aspartate in V. gigantea were observed, demonstrating that the last is more efficient in assimilating urea. The results prompted us to support the idea that V. gigantea, an epiphytic tank bromeliad, is better adapted to absorb and assimilate organic nitrogen, such as urea, while A. comosus, a terrestrial plant, is better adapted to inorganic nitrogen forms, such as ammonium. The natural exposure of tank bromeliads to urea is discussed in the paper.     

Ammonium ion-excreting cyanobacterial mutant as a source of nitrogen for growth of rice: A feasibility study

Summary Growth of rice plants in a nitrogen-free medium was enhanced by inoculation with a nitrogenase-derepressed mutant (strain SA-1) of a cyanobacterium,Anabaena variabilis which excretes NH₄ ⁺ into the medium. Both total dry weight and nitrogen content of rice plants were substantially increased in the presence of the mutant strain but not with the wild type parent, strain SA-0.     

The fetal liver as an alternative stem cell source for hemolymphopoietic reconstitution

In mammalian ontogeny, the liver constitutes the primary hematopoietic organ for some time. Fetal liver cells (FLC) are rich in hematopoietic stem cells with a high proliferative potential but contain few post-thymic T cells. In animal studies, FLC restored hematopoiesis without severe graft-versus-host disease. However, genetic disparity between donor and host frequently limited durable engraftment and prevented or protracted complete immune reconstitution in most fully allogeneic recipients. Some children with severe combined immunodeficiency have been cured by FLC infusion, whereas favorable effects in aplastic anemia, acute leukemia, and inborn errors of metabolism have been limited and badly understood. Fetal liver transplantation in animals may serve as a model for the analysis and management of complications associated with the transfer of purified hematopoietic stem cell grafts and aid in the development of future therapeutic strategies requiring rapidly proliferating stem cell populations.     

Cultivation of bacteria producing polyamino acids with liquid manure as carbon and nitrogen source

Poly(gamma-D-glutamic acid) (PGA)-producing strains of Bacillus species were investigated to determine their ability to contribute to reducing the amount of ammonium nitrogen in liquid manures and their ability to convert some of the ammonium into this polyamino acid as a transient depot for nitrogen. Organisms that do these things should help solve the serious environmental problems which are caused by the use of large amounts of liquid manure resulting from intensified agriculture; these problems are mainly due to the high content of ammonium nitrogen. Bacillus licheniformis ATCC 9945 and Bacillus subtilis were able to grow in liquid manure and to produce PGA in the presence of sodium gluconate. On artificial liquid manure these two strains were able to produce 0.85 and 0.79 g of PGA per liter, respectively. Under conditions that are found in intensified farming situations the ammonia content was reduced within 48 h from 1.3 to 0.75 g/liter. One mutant of B. subtilis 1551 impaired in the catabolism of PGA was obtained after nitrosoguanidine mutagenesis. This mutant produced PGA at a final concentration of 4.8 g/liter, whereas the wild type produced only 3.7 g/liter.     

Cyanuric acid as nitrogen source for micro-organisms

Summary Several fungi, among which species of Penicillium and Hormodendrum (?), were found to utilize cyanuric acid as a nitrogen source, assimilating 66 to 75% of its nitrogen in cell substance. The growth with cyanurate was essentially as good as with ammonia and urea nitrogen. The optimum reaction for growth was around pH 5 to 6, but pH 7 to 8 was suboptimal. No decrease in growth was seen at a cyanurate concentration of 9.3 mM. The triazine ring as such is thus not biologically very stable, and the strong persistance of the triazine herbicides simazine and atrazine must be ascribed to the external substituents and not to the central ring.     

Shoot tips of wheat as an alternative source for regenerable embryogenic callus cultures

Shoot tips of Triticum aestivum L. cvs. Turbo and Nandu, both summer wheat varieties, were excised from 4 and 10 day-old seedlings, and used for induction of embryogenic callus. A modified L3 medium, supplemented with 10 M 2,4-dichlorophenoxyacetic acid (2,4-d) for culture initiation, and 5 M 2,4-d for subculturing, was optimal; 90% of 4 day-old Turbo seedlings formed embryogenic callus. Optimal plant regeneration was achieved from callus incubated on a modified MS medium without 2,4-d, but supplemented with 2.22 M 6-benzylaminopurine and 0.27 M naphthaleneacetic acid. Plantlets formed via embryogenesis from all embryogenic Turbo calli initiated from 4 day-old explants, with a mean number of 8 regenerants per explant. Regeneration occured via embryogenesis only. Results obtained using Nandu were within the same range.Abbreviations BA 6-benzylaminopurine - 2,4-d 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid     

Human amniotic membrane as an alternative source of stem cells for regenerative medicine

The human amniotic membrane (HAM) is a highly abundant and readily available tissue. This amniotic tissue has considerable advantageous characteristics to be considered as an attractive material in the field of regenerative medicine. It has low immunogenicity, anti-inflammatory properties and their cells can be isolated without the sacrifice of human embryos. Since it is discarded post-partum it may be useful for regenerative medicine and cell therapy. Amniotic membranes have already been used extensively as biologic dressings in ophthalmic, abdominal and plastic surgery. HAM contains two cell types, from different embryological origins, which display some characteristic properties of stem cells. Human amnion epithelial cells (hAECs) are derived from the embryonic ectoderm, while human amnion mesenchymal stromal cells (hAMSCs) are derived from the embryonic mesoderm. Both populations have similar immunophenotype and multipotential for in vitro differentiation into the major mesodermal lineages, however they differ in cell yield. Therefore, HAM has been proposed as a good candidate to be used in cell therapy or regenerative medicine to treat damaged or diseased tissues.     

Effects of Ethanolamine as a nitrogen source on hydrogen production by Rhodobacter capsulatus

Ethanolamine was examined as a nitrogen source in the production of hydrogen by Rhodobacter capsulatus ST-410, a hydrogenase-deficient mutant of the strain B-100. It was found that ethanolamine supports cell growth as the sole nitrogen source and permits a large amount of hydrogen evolution, detected at 138 micromol/ml-culture from 3.5 mM ethanolamine and 30 mM DL-malate. The amount corresponded to a stoichiometric yield of 77% and was close to that obtained from 7.0 mM L-glutamate and 30 mM DL-malate. The hydrogen evolution rate per unit biomass (cells) was higher than that with L-glutamate, and the cells grown with ethanolamine had higher nitrogenase activity than the cells grown with L-glutamate. In terms of bioconversion of cellulosic and hemicellulosic biomass to hydrogen, D-glucose, D-xylose, and D-cellobiose were tested as substrates. The results indicated that those sugars permit a large evolution of hydrogen through cultivation with ethanolamine as a nitrogen source. For instance, the cells grown with 3.5 mM ethanolamine evolved hydrogen of 289 micromol/ml-culture (80% yield) from 30 mM D-glucose under a controlled pH of 6.4 to 6.9.     

Microbial fuel cells as an alternative energy source: current status

Microbial fuel cell (MFC) technology is an emerging area for alternative renewable energy generation and it offers additional opportunities for environmental bioremediation. Recent scientific studies have focused on MFC reactor design as well as reactor operations to increase energy output. The advancement in alternative MFC models and their performance in recent years reflect the interests of scientific community to exploit this technology for wider practical applications and environmental benefit. This is reflected in the diversity of the substrates available for use in MFCs at an economically viable level. This review provides an overview of the commonly used MFC designs and materials along with the basic operating parameters that have been developed in recent years. Still, many limitations and challenges exist for MFC development that needs to be further addressed to make them economically feasible for general use. These include continued improvements in fuel cell design and efficiency as well scale-up with economically practical applications tailored to local needs.     

Erythrocytic adenosine monophosphate as an alternative purine source in Plasmodium falciparum

Plasmodium falciparum is a purine auxotroph, salvaging purines from erythrocytes for synthesis of RNA and DNA. Hypoxanthine is the key precursor for purine metabolism in Plasmodium. Inhibition of hypoxanthine-forming reactions in both erythrocytes and parasites is lethal to cultured P. falciparum. We observed that high concentrations of adenosine can rescue cultured parasites from purine nucleoside phosphorylase and adenosine deaminase blockade but not when erythrocyte adenosine kinase is also inhibited. P. falciparum lacks adenosine kinase but can salvage AMP synthesized in the erythrocyte cytoplasm to provide purines when both human and Plasmodium purine nucleoside phosphorylases and adenosine deaminases are inhibited. Transport studies in Xenopus laevis oocytes expressing the P. falciparum nucleoside transporter PfNT1 established that this transporter does not transport AMP. These metabolic patterns establish the existence of a novel nucleoside monophosphate transport pathway in P. falciparum.     

Ammonia as an important nitrogen source for the photosynthetic growth of Rhodospirillum rubrum

The growth of Rhodospirillum rubrum strain K was poor in a glutamatemalate(G-3-X) medium under light-anaerobic conditions. The supplementof ammonia to the G-3-X medium remarkably stimulated the growth.No such stimulation by ammonia was observed under dark-aerobicconditions. The other bacterium, strain M, also showed a similartendency for the ammonia requirement, though its growth in theG-3-X medium was much more abundant as compared to that of strainK. Casamino acid was found to contain stimulating factors for growth.Among the amino acids, arginine and/or histidine were effective.The other factor in casamino acid was found to be ammonia. The crude extracts of strains K and M contained glutamic dehydrogenaseas judged by the formation of glutamate from -ketoglutarateand ammonia. The highly reduced state of the cell componentsunder lightanaerobic conditions, appears to limit the formationof ammonia from glutamate. Ammonia was a preferable nitrogensource to glutamate under the conditions employed. ¹Present address: Institute for Agricultural Research, TohokuUniversity, Sendai. ²Present address: Sanitary Engineering Research Laboratory,Sanitary Engineering Department, Sumitomo Machinery Co. Ltd.,Hiratsuka.     

Hydrolyzed molasses as an external carbon source in biological nitrogen removal

Hydrolyzed molasses was evaluated as an alternative carbon source in a biological nitrogen removal process. To increase biodegradability, molasses was acidified before thermohydrolyzation. The denitrification rate was 2.9-3.6 mg N/g VSSh with hydrolyzed molasses, in which the percentage of readily biodegradable substrate was 47.5%. To consider the hydrolysate as a carbon source, a sequencing batch reactor (SBR) was chosen to treat artificial municipal wastewater. During the 14 days (28 cycles) of operation, the SBR using hydrolyzed molasses as a carbon source showed 91.6 +/- 1.6% nitrogen removal, which was higher than that using methanol (85.3 +/- 2.0%). The results show that hydrolyzed molasses can be an economical and effective external carbon source for the nitrogen removal process.     

Herbivore trampling as an alternative pathway for explaining differences in nitrogen mineralization in moist grasslands

Studies addressing the role of large herbivores on nitrogen cycling in grasslands have suggested that the direction of effects depends on soil fertility. Via selection for high quality plant species and input of dung and urine, large herbivores have been shown to speed up nitrogen cycling in fertile grassland soils while slowing down nitrogen cycling in unfertile soils. However, recent studies show that large herbivores can reduce nitrogen mineralization in some temperate fertile soils, but not in others. To explain this, we hypothesize that large herbivores can reduce nitrogen mineralization in loamy or clay soils through soil compaction, but not in sandy soils. Especially under wet conditions, strong compaction in clay soils can lead to periods of soil anoxia, which reduces decomposition of soil organic matter and, hence, N mineralization. In this study, we use a long-term (37-year) field experiment on a salt marsh to investigate the hypothesis that the effect of large herbivores on nitrogen mineralization depends on soil texture. Our results confirm that the presence of large herbivores decreased nitrogen mineralization rate in a clay soil, but not in a sandy soil. By comparing a hand-mown treatment with a herbivore-grazed treatment, we show that these differences can be attributed to herbivore-induced changes in soil physical properties rather than to above-ground biomass removal. On clay soil, we find that large herbivores increase the soil water-filled porosity, induce more negative soil redox potentials, reduce soil macrofauna abundance, and reduce decomposition activity. On sandy soil, we observe no changes in these variables in response to grazing. We conclude that effects of large herbivores on nitrogen mineralization cannot be understood without taking soil texture, soil moisture, and feedbacks through soil macrofauna into account.