Nucleotide sequence of the Bacillus subtilis trpE and trpD genes

Several overlapping portions of the tryptophan (trp) operon of Bacillus subtilis have been cloned into plasmid pBR322. The nucleotide sequence of the region comprising the trpE and trpD genes and a portion of the trpC gene has been determined. When the deduced amino acid sequences of these genes are compared with their counterparts in Escherichia coli, several regions of striking homology are seen. The probable initiation codons for the trpE, D and C genes are each preceded by a recognizable Shine-Dalgarno sequence. The coding sequences for the trpE and trpD genes and for the trpD and trpC genes overlap slightly, leaving no intercistronic regions between the genes.     

Essential fatty acids and phosphorus in seston from lakes with contrasting terrestrial dissolved organic carbon content

1. It is often assumed that lakes highly influenced by terrestrial organic matter (TOM) have low zooplankton food quality because of elemental and/or biochemical deficiencies of the major particulate organic carbon pools. We used the biochemical [polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA) – 20:5ω3] and elemental (C : P ratio) composition of particulate matter (PM) as qualitative measures of potential zooplankton food in two categories of lakes of similar primary productivity, but with contrasting TOM influence (clear water versus humic lakes). 2. C : P ratios (atomic ratio) in PM were similar between lake categories and were above 400. The concentration (μg L⁻¹) and relative content (μg mg C⁻¹) of EPA, as well as the particulate organic carbon concentration, were higher in the humic lakes than in the clear‐water lakes. 3. Our results show high fatty acid quality of PM in the humic lakes. The differences in the biochemical quality of the potential zooplankton food between lake categories can be attributed to the differences in their phytoplankton communities. 4. High biochemical quality of the food can result in high efficiency of energy transfer in the food chain and stimulate production at higher trophic levels, assuming that zooplankton are able to ingest and digest the resource available.     

Osmium ammine-B and electron spectroscopic imaging of ribonucleoproteins: Correlation of stain and phosphorus

Summary— Ultra-thin sections of Chironomus salivary glands were stained in a non-Feulgen procedure with osmium ammine-B and imaged at several electron energy-loss windows. For two types of RNP-containing structures (ie Balbiani ring granules and endoplasmic reticulum), a significant spatial correlation was observed between stain distribution and net phosphorus distribution. Non-Feulgen osmium ammine-B staining does not require the use of ultra-thin sections and can approximate the distribution of nucleic acid phosphorus.     

Effects of phosphorus on the morphology of VA mycorrhizal root system of leek (Allium porrum L.)

Leek plants were raised on sterilized soil/sand medium amended with Ca(H₂PO₄)₂. H₂O ranging up to 750 mg Pkg⁻¹. Addition of P increased total root length by increasing the initiation of laterals, which extended at a constant rate. This change in root growth was paralleled by the P inflow into the plant, but not by the P concentration of the plant, suggesting that it is the rate of P uptake which affects root branching.     

Effects of light and nutrients on the net accumulation and elemental composition of epilithon in boreal lakes

1. Two experiments in the Experimental Lakes Area (ELA) in north-western Ontario, Canada examined the effects of light and two key elements on the net accumulation and elemental composition of epilithon. In Lake (L) 224, benthic algae were grown under different light intensity and phosphorus supply, while in L302S we provided three levels of two different carbon sources (bicarbonate and glucose) to algae colonizing nutrient-diffusing substrata. After 1 month of accumulation, we sampled biofilms for chlorophyll (chl), carbon (C), phosphorus (P) and algal C.
2. Increased C supply did not significantly affect algal growth (C or chl) or elemental composition (C/P ratios) in L302S. However, P enrichment increased chl and algal C, dramatically reduced the C/P ratio of epilithon, and did not affect total organic C in L224. Phosphorus enrichment also increased the proportion of algal material in the total particulate organic matter and altered the taxonomic composition of algae in L224 biofilms. Shading had no significant effect on the C/P ratio and total organic C in epilithon from the L224 experiment.
3. Our results demonstrate that P supply affects the elemental composition of organic matter that collects on rock substrata. It thus appears that low availability of P relative to C and light drives the formation and retention of high C/P organic matter on rock surfaces in oligotrophic boreal lakes.     

Trophic transfer of biodiversity effects: functional equivalence of prey diversity and enrichment?

Producer diversity is frequently assumed to be detrimental to herbivores, because less edible taxa are more likely to dominate diverse communities. Many producers are, however, complementary in their resource use, and primary production is often positively related to producer diversity. We performed an experiment with microalgae and a generalist herbivore to explore the hypothesis that such positive effects are transferred up the food chain and are functionally comparable to effects of enrichment with a limiting resource. In both absence and presence of grazers, primary production was positively affected by both light supply and producer diversity. Survival, reproduction, and biomass of herbivores were also positively affected by light supply and producer diversity, with both factors contributing equally to grazer performance. We conclude that producer diversity can indeed have similar positive effects on secondary production as enrichment with a limiting resource and discuss conditions under which such positive effects are likely to dominate over negative ones.     

Phosphorus distribution inside Chinese fir seedlings under different P supplies based on 32P tracer

通过分析杉木(Cunninghamia lanceolata)幼苗磷(P)分配规律, 可以阐明两个磷高效利用杉木在不同供磷水平下吸收外源磷的分配及动态变化, 为进一步进行磷高效利用基因型的选育提供参考。该研究以2个磷高效利用杉木家系(被动忍受型M1与主动活化型M4)幼苗为试验材料, 利用 ³²P同位素示踪技术, 研究在不同供磷水平下2个杉木家系幼苗磷分配规律。结果表明, M1和M4吸收的外源磷的含量分布特征均为根>叶>茎, 自显影中相同处理时期的各器官在水平投影面上 ³²P含量均为根>茎>叶。低磷处理下M1和M4根、茎、叶吸收的外源磷的含量均明显低于高磷处理, 自显影中相同处理时间根、茎、叶低磷水平下成像的黑化程度也低于高磷水平, 且低磷处理下吸收的外源磷的含量增加缓慢, 说明低磷胁迫严重影响杉木苗磷的吸收与积累。M1和M4的根系磷分配率在低磷胁迫下呈现出明显的先减少后增加趋势, 高磷水平下根系磷分配率表现为先增加后趋于平稳。这说明M1和M4可以通过体内磷的重新分配来适应外界低磷胁迫, 即杉木苗在低磷胁迫初期将根系中的磷转移至地上部分, 随着胁迫时间的延长, 地上部分的磷向根系中转移。但两个家系在低磷条件下对吸收的外源磷的分配格局差异明显: 从开始至结束M1吸收的外源磷的分配率表现为根系>地上部分, 而M4先表现为根系>地上部分, 后表现为地上部分>根系, 说明M1在低磷胁迫后加强体内磷循环的程度相比于M4更高, 即磷从地上部分向根系转移的趋势更强烈。     

Phytochemical Profile and Anti-Inflammatory Activity of the Fraction from Artemisia lavandulaefolia

Artemisia lavandulaefolia, a traditional herbal medicine, has been utilized as anti-inflammatory and analgesia agent in clinic. Bioassay-guided fractionation resulted in a fraction (ALDF) with anti-inflammatory effect obtained from A. lavandulaefolia. Its main constituents were analyzed and identified by UPLC-ESI-Q-TOF-MS technology. ALDF showed the strong inhibitory activity on the nitrogen oxide (NO) production in LPS-induced RAW 264.7 macrophages with an IC₅₀ value of 1.64±0.41 μg/mL. Further results displayed that ALDF also significantly suppressed the secretion of key pro-inflammatory mediators, including tumor necrosis factor-α (TNF-α), prostaglandin E₂ (PGE₂) and interleukin-1β (IL-1β), and the increase of the inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression induced by LPS stimulation. Mechanism study indicated that ALDF was able to block NF-κB signaling pathway through inhibiting IκB and p65 phosphorylation, as well as NF-κB p65 nuclear translocation. Furthermore, in vivo results in mice revealed that treatments with ALDF evoked significant inhibition on ear edema induced by xylene and on the writhing responses induced by acetic acid. These results suggest that ALDF holds great potential in the prevention and treatment of inflammatory disorders.