Сверхлегкие генераторные модули для КВЧ-терапии

Разработаны миниатюрные генераторные модули для КВЧ-терапии, лег-ко фиксируемые в любом месте тела пациента. Могут быть использованы не только в медицине

Biosynthesis of Random-Homo Block Copolymer Poly[Glycolate-ran-3-Hydroxybutyrate (3HB)]-b-Poly(3HB) Using Sequence-Regulating Chimeric Polyhydroxyalkanoate Synthase in Escherichia coli

Glycolate (GL)-containing polyhydroxyalkanoate (PHA) was synthesized in Escherichia coli expressing the engineered chimeric PHA synthase PhaC(AR) and coenzyme A transferase. The cells produced poly[GL-co-3-hydroxybutyrate (3HB)] with the supplementation of GL and 3HB, thus demonstrating that PhaC(AR) is the first known class I PHA synthase that is capable of incorporating GL units. The triad sequence analysis using H-1 nuclear magnetic resonance indicated that the obtained polymer was composed of two distinct regions, a P(GL-ran-3HB) random segment and P(3HB) homopolymer segment. The random segment was estimated to contain a 71 mol% GL molar ratio, which was much greater than the value (15 mol%) previously achieved by using PhaC1(P)(s)STQK. Differential scanning calorimetry analysis of the polymer films supported the presence of random copolymer and homopolymer phases. The solvent fractionation of the polymer indicated the presence of a covalent linkage between these segments. Therefore, it was concluded that PhaC(AR) synthesized a novel random-homo block copolymer, P(GL-ran-3HB)-b-P(3HB)

Impacts of organic residue management in Eucalyptus forest on microbial communities

Harvest residue management during inter-rotation period greatly influences the availability ofnutrients in the soils and the sustainability of future rotations in fast growing plantations establishedon highly weathered tropical forest. Impact of forest management treatment on productivity was shown, particularly in plantations where organic matter (OM) content is extremely low like in Congo. Consequences of OM management on microbial communities were rarely taken in account. However, changes in microbial biodiversity can impact decomposition processes indicating that understanding the significance of biodiversity is essential to assess the consequences of forestry practices for carbon and nutrient cycles. Experiment was conducted in Eucalyptus plantations in Congo. Three treatments were studied (all aboveground organic residuesremoved from the plot; only stemwood harvested which correspond to Congolese commercial plantation; or double supply of residues). DNA and RNA were co-extracted from leaf-litter and upper soil layers (0-10 cm). Density and structure of bacterial and fungal communities were assessed by the quantitative PCR (qPCR) and fingerprinting technique (DGGE), respectively based on 16S and 18S rRNA. We also investigated functional microbial communities potentially involved in C cycling: the phylum of the Actinobacteria, known for their saprophytic activities; the BphDox bacterial community involved in the degradation of aromatic compounds and Laccase fungal community implicated in the degradation of phenolic compounds. Altogether, these dataallowed to progress in the establishment of links between nutrients flux measured in field and microbial analyses which is a challenge to a better understanding of the functioning of forest ecosystems

Introducing N2-fixing trees (Acacia mangium) in eucalypt plantations rapidly modifies the pools of organic P and low molecular weight organic acids in tropical soils

Many studies have shown that introducing N2-fixing trees (e.g. Acacia mangium) in eucalypt plantations can increase soil N availability as a result of biological N2 fixation and faster N cycling. Some studies have also shown improved eucalypt P nutrition. However, the effects of N2-fixing trees on P cycling in tropical soils remain poorly understood and site-dependent. Our study aimed to assess the effects of planting A. mangium trees in areas managed over several decades with eucalypt plantations on soil organic P (Po) forms and low molecular weight organic acids (LMWOAs). Soil samples were collected from two tropical sites, one in Brazil and one in the Congo. Five different treatments were sampled at each site: monospecific acacia, monospecific eucalypt, below acacias in mixed-species, below eucalypts in mixed-species as well as native vegetation. Po forms and LMWOAs were identified in sodium hydroxide soil extracts using ion chromatography and relationships between these data and available P were determined. At both sites, the concentrations of most Po forms and LMWOAs were different between native ecosystems and monospecific eucalypt and acacia plots. Also, patterns of Po and LMWOAs were clearly separated, with glucose-6-P found mainly under acacia and phytate and oxalate mainly under eucalypt. Despite the strongest changes occurred at site with a higher N2 fixation and root development, acacia introduction was able to change the profile of organic P and LMWOAs in <10 years. The variations between available Pi, Po and LMWOA forms showed that P cycling was dominated by different processes at each site, that are rather physicochemical (via Pi desorption after LMWOAs release) at Itatinga and biological (via organic P mineralization) at Kissoko. Specific patterns of Po and LMWOAs forms found in soil sampled under acacia or eucalypt would therefore explain the effect of acacia introduction in both sites

Potential of Bioassays to Assess Consequences of Cultivation of <i>Acacia mangium</i> Trees on Nitrogen Bioavailability to <i>Eucalyptus</i> Trees: Two Case-Studies in Contrasting Tropical Soils

We hypothesized that the nitrogen-fixing tree Acacia mangium could improve the growth and nitrogen nutrition of non-fixing tree species such as Eucalyptus. We measured the N-mineralization and respiration rates of soils sampled from plots covered with Acacia, Eucalyptus or native vegetation at two tropical sites (Itatinga in Brazil and Kissoko in the Congo) in the laboratory. We used a bioassay to assess N bioavailability to eucalypt seedlings grown with and without chemical fertilization for at least 6 months. At each site, Eucalyptus seedling growth and N bioavailability followed the same trends as the N-mineralization rates in soil samples. However, despite lower soil N-mineralization rates under Acacia in the Congo than in Brazil, Eucalyptus seedling growth and N bioavailability were much greater in the Congo, indicating that bioassays in pots are more accurate than N-mineralization rates when predicting the growth of eucalypt seedlings. Hence, in the Congo, planting Acacia mangium could be an attractive option to maintain the growth and N bioavailability of the non-fixing species Eucalyptus while decreasing chemical fertilization. Plant bioassays could help determine if the introduction of N2-fixing trees will improve the growth and mineral nutrition of non-fixing tree species in tropical planted forests

Organic phosphorus immobilization in microbial biomass controls how N2-fixing trees affect phosphorus bioavailability in two tropical soils

International audienceEucalyptus is the tree most widely planted in tropical countries to satisfy growing demand for wood products, but high yields require high fertilizer inputs. Introducing N 2-fixing trees (NFT), such as Acacia mangium, has been proposed to improve soil fertility and aboveground tree biomass in Eucalyptus plantations. In addition to N inputs, NFT species may increase plant P nutrition through increased rates of organic P (Po) cycling. However, the positive effect of acacia on soil P availability and plant P nutrition was found to vary substantially between sites. The ability of acacia to improve P bioavailability might mainly depend on Po sequestration in microbial biomass, preventing Po mineralization by phosphatases and efficient Po recycling. This hypothesis was tested at two tropical sites, Itatinga (Brazil) and Kissoko (Congo) by measuring inorganic phosphate (Pi), Po and enzyme-labile Po in bicarbonate extracts from the topsoil collected from plots with Eucalyptus, acacias, or native vegetation. We used bicarbonate enzyme-labile Po after soil autoclaving as an indicator of microbial Po, and a Eucalyptus bioassay to measure the actual P bioavailability for Eucalyptus seedlings. At Itatinga, bicarbonate-Pi was very low, while Po was the main P form. Enzyme-labile Po was very weak in intact soils and high in autoclaved soils, indicating high immobilization in microbial biomass. At Kissoko, Po was highly enzyme-labile in both intact and autoclaved soils, especially from acacia plots, suggesting very low Po immobilization in microbial biomass. Growth and P accumulations in Eucalyptus seedlings were low in all soils at Itatinga and were the highest in Eucalyptus plants grown in acacia soils at Kissoko. Our results highlight the potential of acacia trees for improving P bioavailability for other tree species if labile Po enrichment in the soil provided by this N 2-fixing tree is not locked into the microbial biomass