Phylogeny and nitrogen fixation potential of Bradyrhizobium species isolated from the legume cover crop Pueraria phaseoloides (Roxb.) Benth. in Eastern Cameroon

Pueraria is an herbaceous, perennial legume crop originating in Asia. Pueraria phaseoloides (Roxb.) Benth. (tropical kudzu) is frequently introduced into production systems and is used as green manure, a cover crop and a forage plant, making it important economically. We used P. phaseoloides as a trap crop to study and characterize soil rhizobia in Eastern Cameroon. Bacteria were isolated from fresh nodules collected from field-grown P. phaseoloides roots. The 16S-23S rRNA internal transcribed spacer (ITS) sequences from 30 bacterial isolates were amplified by polymerase chain reaction (PCR) and the reaction products were sequenced. Phylogenetic analysis revealed that all isolates were ascribed to the genus Bradyrhizobium and were grouped into three clusters of Bradyrhizobium sp. strains, one cluster of B. yuanmingense strains, and one cluster of B. elkanii strains. Acetylene reduction assay (ARA) results indicated that the B. yuanmingense strains had significantly higher nitrogen fixation potential and that they could be used as inoculants to enhance nitrogen fixation in Pueraria grown in Eastern Cameroon.     

CO2稀释对生物质燃气燃烧与排放特性的影响

在一台火花点火发动机上,分别进行了CO2稀释对生物质燃气中可燃组分CH4、CO和H2的燃烧及排放性能影响的试验研究。研究结果表明,稀释燃烧能够有效降低NOx排放量;适当的稀释率对发动机的平均有效压力、循环变动以及热效率的影响较小,但过大的稀释率会导致部分燃烧。通过CO2稀释燃烧的手段,可以得到生物质燃气以一定热效率和NOx排放水平为指标的适宜燃料条件范围。     

Temperature during grain ripening affects the ratio of type-II/type-I protein body and starch pasting properties of rice (Oryza sativa L.)

The starch and protein properties of rice grain are important factors for sake brewing and these properties are reported to be influenced by temperatures during grain ripening. Amylose content, nitrogen content, protein composition, pasting properties measured by a Rapid Visco Analyser (RVA), and their relationship to temperatures during ripening were investigated in a rice cultivar, Yamadanishiki, which was grown under various conditions in the same experimental field. The average temperature after heading was significantly correlated with amylose content and RVA properties, but not with nitrogen content. Under high temperatures during ripening, a decrease in prolamin, which accumulated in type I protein body (PB-I), and an increase in glutelin, which deposits in type II PB (PB-II), were recognized. The ratio of PB-II/PB-I and RVA pasting temperatures were distinctly increased as the temperature became higher. High temperatures during grain ripening would lead to difficulties in digesting steamed rice grains by Aspergillus oryzae, together with ease in digesting rice protein. The average temperature of 11–20 days after heading showed a higher correlation coefficient than that of 1–10 or 21–30 days, implying that temperatures during the middle stage of grain development would be important in determining the rice component that relates to brewing properties.     

Comparison of soil physical properties in evergreen and deciduous forests in central Cambodia

We investigated soil physical properties in three forest types in tropical lowland monsoon forests in central Cambodia under the same climatic conditions, i.e., Kanhaplic Haplustults in dry evergreen forest (KH-E), Arenic Haplustults in dry deciduous forest (AH-D), and Arenic Ultic Alorthods in mixed evergreen–deciduous forest (AA-M), to clarify the relationship between forest types and soil physical properties. The clay content was correlated with water content at ψ = −9.8 and −1500 kPa (WC10 and WC1500), available water capacity (AWC), and the van Genuchten (vG) parameter N (P < 0.01). vG parameter N was in the order AH-D > AA-M > KH-E whereas vG parameter α had a high value in KH-E soil at 0–100 cm in depth. The cumulative AWC (AWCcl, mm) at a soil depth of 0–200 cm was higher in the AH-D than in the KH-E, and was not considered a major factor affecting the distribution of different forest types under the same climatic conditions. The unsaturated hydraulic conductivity (K) at 0–100 cm in depth, estimated by use of models, was higher in AH-D than in KH-E mostly at matric potential ψ > −10 kPa. The low K in KH-E at ψ > −10 kPa was considered favorable for evergreen trees to retain the soil water for the transpiration in the dry season, and the matric potential in KH-E showed more gentle decreases in the early dry seasons than AH-D. Thus the differences in K among generally sandy soil types could possibly affect the establishment of different forest types in the study area with the same climate.     

Use of <Emphasis Type="Italic">Porphyra</Emphasis> spheroplasts as feed additive for red sea bream

ABSTRACT:   Two test diets with and without 5% Porphyra spheroplasts (PS) were formulated using white fishmeal as the main protein source. Red sea bream Pagrus major (mean body weight 15.4 ± 0.1 g) were maintained in a flow-through system (100 L) of thermo-controlled sea water (salinity 32–34, 25°C, 8 L/min) with ordinary aeration (400–600 mL/min) under laboratory light conditions (light–dark 12 h:12 h). Fish were fed three times a day at 10:00, 14:00 and 18:00 hours by hand for 42 days at 6% body weight on each experimental diet. Studies revealed that growth performance, survival and nutrient retention were significantly ( P  < 0.05) higher in the groups fed a diet containing spheroplasts (PS diet). Further, the fish fed the PS diet showed significantly ( P  < 0.05) lower feed conversion rates. Both groups of the PS and control diets had similar levels of body nutritional profile in terms of proximate compositions and fatty acids without compromising blood serum related parameters. From these experimental results, thus, it is comprehensible that a supplementary diet containing Porphyra spheroplasts can be used for maximizing not only growth of P. major but also for utilization of the feed ingredients.     

Dietary supplementation of red alga Pyropia spheroplasts on growth,feed utilization and body composition of sea cucumber,Apostichopus japonicus (Selenka)

A feeding experiment was conducted in a closed recirculating system to evaluate the effects of freeze‐dried spheroplasts prepared from Pyropia yezoensis (Ueda) on feed intake, growth and biochemical composition of sea cucumber, Apostichopus japonicus (Selenka). Pyropea spheroplasts (PS) were prepared through enzymatic treatment to break down the complex mixture of polysaccharides cell walls that might be easier for growth energy partitioning. Sea cucumbers were fed‐formulated diets with 10 (Diet 1), 30 (Diet 2) and 50 g/kg (Diet 3) inclusion level of PS. A diet without PS was used as a control (Diet 4). The experiment was conducted for 6 weeks maintaining water temperature 15 ± 1°C, photoperiod 18:06 hours (D:L). Feed was supplied ad‐libitum at 16.00 h once in a day, and the remaining feed and faeces were removed in the next day. Results showed that the highest growth was observed in the 50 g/kg PS diet compared to other treatments. Total weight gain, mean weight gain, net yield, protein efficiency ratio (PER) and protein gain (%) were significantly higher in the 50 g/kg PS diet (p < .05). A significantly higher percentage of energy was allocated for growth in the 50 g/kg PS diet. The highest specific growth rate and feed conversion efficiency (p < .05) were observed in the higher percentage of PS diet. Both the growth performance and biochemical analysis showed that superior growth was observed with increasing levels of PS in the diet. We infer that PS can be used as a new, cheaper feed ingredient in the formulated diet of A. japonicus.     

Epizootiological survey of hantavirus among rodent species in Ningxia Hui Autonomous Province, China

Hantaviral antibodies were detected in the sera from Apodemus (A.) agrarius and A. peninsulae captured in Ningxia province, China by several different serological diagnostic methods. A total of 409 sera from rodent and insectivore species were collected in 1999 and examined by indirect immunofluorescent antibody assay (IFA). Among them, 19 of 191 (9.9%) sera of A. agrarius and 1 of 13 (7.7%) sera of A. peninsulae were positive for hantaviral antibodies. The other species (Rattus norvegicus, Mus musculus, Cricetulus triton, and Sorex cylindricauda) were negative. The reaction pattern of positive serum was characterized as scattered and granular virus antigens in the cytoplasm of hantavirus infected Vero E6 cells. Some of the A. agrarius sera positive for hantavirus were further examined by Western blotting (WB), enzyme-linked immunosorbent assay (ELISA), and the focus reduction neutralization test (FRNT). By WB, positive sera showed the same specific reaction pattern of baculovirus-expressed recombinant hantaviral nucleocapsid protein, as shown in hantavirus-immune serum. By ELISA, IFA-positive sera showed significantly higher optical densities (around 1.0) than the negative A. agrarius sera. Hantaan type hantavirus was neutralized with the positive sera. These results suggest that A. agrarius have hantavirus infection and may play a role as a reservoir animal for hantavirus in Ningxia Hui Autonomous Province, China.     

Soil phosphorus of stable fraction differentially associate with carbon in the tropical forest and savanna of eastern Cameroon

ABSTRACT

The forest–savanna transition zone, which contains nutrient-poor soils (Oxisols), is found throughout central Africa. To evaluate the effect of deforestation on soil phosphorus dynamics, which regulate the plant growth in this area, we quantified the relationship between phosphorus (P) and carbon (C) in different fractions and compared their relationship to forest and savanna (deforested vegetation) in eastern Cameroon. We analyzed the P, C, and nitrogen (N) contents of soil using the physical fractionation method (0.25–2.0 mm as macro-particulate organic matter [M-POM]; 0.053–0.25 mm as micro-POM; and <0.053 mm as Clay+silt) in different land management (young and old forests and annual and perennial grass savannas at 100-cm soil depth). We found larger soil P stock in forests (4.7–4.9 Mg P ha^?1) than that in savannas (3.4–4.0 Mg P ha^?1), though soil C and N stocks were similar between the vegetation. We also observed lower soil P stock in the active fraction (M-POM) with its higher C:P and lower C:N ratio in forest surface layer (0–10 cm), indicating that forests have lower available soil P. By using the regression analysis, we found a clear relationship between P and C in the stable fraction (Clay+silt) of the upper layer (0–40 cm) for each land management, and the coefficient of the regression was clearly different between the forest and savanna. It indicates that a more chemically complex organic P form of the stable fraction exists in forest soil than in savanna soil. These results indicate that the deforestation (savannazation) affect the active and stable P dynamics and it should cause the lower soil P stock of the upper layer in savanna than in forest.     

Deep rooting in winter wheat: rooting nodes of deep roots in two cultivars with deep and shallow root systems

Deep rooting of wheat has been suggested that it influences the tolerance to various environmental stresses. In this study, the nodes from which the deepest penetrated roots had emerged were examined in winter wheat. The wheat was grown in long tubes with or without mechanical stress and in large root boxes. The length and growth angle of each axile root were examined to analyze the difference in the vertical distribution of the roots between the two wheat cultivars, one with a deep and one with a shallow root system. In Shiroganekomugi, a Japanese winter wheat cultivar with a shallow root system, the rooting depths of the seminal and nodal roots decreased as the rooting nodes advanced acropetally. Six out of nine deepest roots were seminal root in the non-mechanical stress conditions. In Mutsubenkei, a Japanese winter wheat cultivar with a deep root system, grown in root boxes, not only the seminal roots but also the coleoptilar and the first nodal roots penetrated to a depth of more than 1.3 m in the root box, and became the deepest roots. In both cultivars, the seminal roots became the deepest roots under the mechanical stress conditions. There were no clear tendencies in the root growth angles among the rooting nodes in the wheat root system. This indicates that the length of the axile roots can explain the differences in the rooting depths among axile roots in a wheat root system. On the other hand, the axile roots of Mutsubenkei elongated significantly more vertically than those of Shiroganekomugi. This suggests that not only seminal but also nodal roots exhibit strong positive gravitropism and penetrate deeply in a cultivar with a deep root system. In wheat cultivars, it is likely that the extent of its Root Depth Index results partly from the gravitropic responses of both seminal and nodal roots.     

Biological activities of synthetic grammistins and analogous peptides

Grammistins, peptide toxins isolated from the skin secretions of two species of soapfishes Grammistes sexlineatus and Pogonoperca punctata, are new members of the family of linear membrane-lytic antibacterial peptides characterized by the abundance of amphiphilic α-helices. As the first step toward future use of grammistins to examine the mode of membrane lysis and design new antibiotics, C-terminally free and amidated forms were chemically synthesized for each of five grammistins (Gs 1, Gs 2, Pp 1, Pp 2b and Pp 3), and evaluated for hemolytic and antibacterial activities. No difference in biological activities was observed between C-terminally free and amidated forms of Gs 1, while the C-terminally amidated forms of the other grammistins exhibited much higher activities than the C-terminally free forms. Comparison with the biological activities of natural grammistins, together with our preliminary cloning experiments, showed that natural grammistins, except for Gs 1, are C-terminally amidated. As for Pp 1, six analogous peptides were further synthesized. Determination of their biological activities revealed that the amphiphilic α-helical structure and positive charge are important for the hemolytic and antibacterial activities, respectively, of Pp 1.