Interactions between the tobacco budworm,Heliothis virescens,and the δ-endotoxin produced by the HD-1 isolate of Bacillus thuringiensis var. kurstaki: Relationship between length of exposure to the toxin and survival

Larvae of the tobacco budworm, Heliothis virescens, which were fed ad libitum for 24, 48, and 72 hr on a diet treated with various levels of the δ-endotoxin produced by the HD-1 isolate of Bacillus thuringiensis var. kurstaki and then transferred to an untreated diet, showed an unexpected capacity to recover from the effects of the toxin, although, as the length of exposure increased, the capacity decreased. Observations on larvae held to emergence indicated that recovery from the toxin was complete. X-ray studies using Ba²⁺ incorporated into the diet showed that, although the toxin paralyzed the midgut of the treated animals, many animals recovered after the toxin was removed, with food once again passing through the gut.     

NF-κB对PPARδ基因的转录调控

过氧化物酶体增殖因子活化受体δ基因(PPARδ)与结直肠癌相关,但其转录调控机制尚不清楚.本研究构建了PPARδ基因的启动子荧光素酶报告基因载体,用删除法定位了启动子活性区域,并通过核酸重叠法和电泳迁移率变更实验,将该区域缩小到30 bp,预测该区域可能起作用的转录因子结合位点;通过启动子定点突变分析和核酸诱骗实验,发现真正起作用的是-156～-127区域内NF-κB的结合位点.电泳迁移率变更法和超迁移分析实验,证实NF-κB能够与该区域结合,并且在抑制NF-κB的DNA结合活性后,PPARδ mRNA的表达明显降低.这些实验表明,在Lovo细胞中,转录因子NF-κB参与了PPARδ的表达调控.     

Biotoxicity assessment of cloned cry 11 protein gene from Bacillus thuringiensis 9NF

The current investigation describes the isolation and characterization of toxic Bt. local isolates harboring 99% homology with Bti. prototoxin Bacillus thuringiensis (AXJ97553.1 and novel OUB27301.1) which contains full length cry11 gene (1.9 kb). Initially, it was cloned in pTZ57R/T and then sub-cloned in pET30a(+) for expression. The optimized conditions for good expression were found 1 mM IPTG, 3.5–4 h incubation time, and 37 °C. Toxicological assays were determined against 3rd instar larvae of Aedes aegypti with expressed partially purified and crude recombinant protein using recombinant E. coli BL21, DE3 transformed with cry11 gene. It was found that partially purified Bt. protein is highly toxic against A. aegypti larvae with LC₅₀ value of 42.883 ± 6 µg/ml. B. thuringiensis strains producing Cry 11 toxic protein can be used as biopesticide to control resistance in insects.     

Phospholipase C delta-type consists of three isozymes: bovine PLCdelta2 is a homologue of human/mouse PLCdelta4

To date, 12 phospholipase C (PLC) isozymes have been identified in mammals, and they are divided into five classes, beta-, gamma-, delta-, epsilon-, and zeta-type. PLCdelta-type is reported to be composed of four isozymes, PLCdelta1-delta4. Here we report that a screening for mouse PLCdelta2 from a BAC library with primers that amplify a specific region of bovine PLCdelta2 resulted in isolation of one clone containing the mouse PLCdelta4 gene. Furthermore, a database search revealed that there is only one gene corresponding to PLCdelta2 and PLCdelta4 in the mouse and human genomes, indicating that bovine PLCdelta2 is a homologue of human and mouse PLCdelta4. However, PLCdelta2 Western blot analysis with a widely used commercial anti-PLCdelta2 antibody showed an expression pattern distinct from that of PLCdelta4 in wild-type mice. In addition, an 80-kDa band, which was recognized by antibody against PLCdelta2, was smaller than an 85-kDa band detected by anti-PLCdelta4 antibody, and the 80-kDa band was detectable in lysates of brain, testis, and spleen from PLCdelta4-deficient mice. We also found that immunoprecipitates from brain lysates with this PLCdelta2 antibody contained no PLC activity. From these data, we conclude that bovine PLCdelta2 is a homologue of human and mouse PLCdelta4, and that three isozymes (delta1, delta3, and delta4) exist in the PLCdelta family.     

A putative second messenger of insulin action regulates hepatic microsomal glucose-6-phosphatase

Physiological concentrations of insulin suppressed rat liver microsomal glucose-6-phosphatase activity in vitro. To attest a hypothesis that a putative second messenger of insulin action (insulin mediator) mediated this process, we isolated the low molecular factor from insulin-treated plasma membranes of rat liver, which was acid- and heat-stable substance of a peptide nature. The insulin mediator which was proved to activate the mitochondria pyruvate dehydrogenase suppressed microsomal glucose-6-phosphatase. The insulin mediator was linked to suppression of the gluconeogenic enzyme through the control of non-specific phosphohydroxylase.     

Toxicity of Bacillus thuringiensis entomocidal protein toward cultured insect tissue

The entomocidal protein from crystalline inclusion bodies of Bacillus thuringiensis can be bioassayed in vitro using cultured insect tissue. Larval cells of the spruce budworm, Choristoneura fumiferana, are damaged by enzyme-digested (activated) protein isolated from B. thuringiensis crystals. Measurement of toxicity is accomplished by detection of adenosine triphosphate (ATP) in treated cultures using firefly bioluminescence. The ATP content of toxin-treated tissue is inversely proportional to the amount of toxin added. Tissue cells from the spruce budworm exhibited maximum susceptibility to activated δ-endotoxin after 120 hr incubation. Probit analysis of tissue ATP response to toxin dose indicated 50% of the cells were damaged by 14.6 μg or less of toxin protein per 2 × 10⁵ insect tissue cells. Activated δ-endotoxin was entomocidal to insects as well, as detemined by mortality studies with second-instar larvae of the European corn borer. Electron microscopic observations of insect tissue treated with activated δ-endotoxin protein for 60 min revealed massive outer membrane disruption and subsequent loss of cytoplasmic constituents, accompanied by swelling of the nuclear membrane.     

Natal origins and timing of migration of two passerine species through the southern Alps: inferences from multiple stable isotopes (δ2H, δ13C, δ15N, δ34S) and ringing data

Understanding spatial linkages between areas used by migratory animals during the annual cycle is fundamental to their conservation. Stable isotope measurements of animal tissues can be a valuable tool in understanding spatial connectivity and migration phenology of migratory wildlife. We inferred natal origins of two migratory passerines, European Pied Flycatcher Ficedula hypoleuca and European Robin Erithacus rubecula, captured during autumn migration in the Italian Alps, by combining feather δ²H (δ²H_f) and ring recovery data. We used a spatially explicit likelihood-based method to assign individuals to a precipitation δ²H surface calibrated to represent feather δ²H, together with the directional probability of origin from ring recoveries. The highest probabilities of origin for most individuals of both species were in central and north-eastern Europe. Seasonal trends in δ²H_f, which described the species’ migratory phenology through the Italian Alps, were correlated with feather δ¹³C, δ¹⁵N and δ³⁴S values, indicating strong spatial discrimination related to continental patterns for these isotopes. We demonstrate how this combined information can define catchment areas and migratory connectivity of birds intercepted in the Alps. We highlight the importance of ringing data in defining directional priors to define Bayesian-based probability surfaces using continental δ²H_f isoscapes, and how such information can be used to inform estimates of migratory connectivity.     

Regulation of mitochondrial biogenesis: yeast mutants deficient in synthesis of delta-aminolevulinic acid

A new class of Saccharomyces cerevisiae mutants deficient in biosynthesis of all cytochromes was isolated from cultures grown in medium containing ethidium bromide. Cytochrome c synthesis may be restored to normal by growing mutant cells in medium supplemented with δ-aminolevulinic acid. Cytochrome deficiency results from mutation in two genetic determinants, one nuclear, the other mitochondrial. When cells possess normal (ρ⁺) mitochondrial DNA, expression of the abnormal nuclear determinant (cyd-1) is largely masked, so that cells can grow on glycerol as primary carbon source and all cytochromes are present. Nevertheless, the presence of the cyd-1 mutation may be detected in ρ⁺ strains, since synthesis of all cytochromes is enhanced to some extent by δ-aminolevulinic acid. Destruction of mitochondrial DNA unmasks the underlying defect so that cyd-1 ρ^? strains are almost completely lacking in detectable cytochromes. Although spectra of cyd-1 ρ⁺ strains resemble those of cytochrome c (cyc) mutants, cyd-1 mutants represent a new complementation group different from six known cyc groups. Cytochrome c biosynthesis in only one of these six types of cytochrome c mutants, cyc4-1, was restored to normal by δ-aminolevulinic acid. Therefore, since cyc4-1 and cyd-1 are complementary, and segregate independently, δ-aminolevulinic acid synthesis appears to be controlled by at least two nuclear genes, and by one or more genes located in mitochondrial DNA. Glycine does not replace δ-aminolevulinic acid in stimulating cytochrome biosynthesis in cyd-1 or cyc-4 mutants. A regulatory system involving exchange of information between mitochondria and the nuclear-cytosolic compartment is indicated by the results. Studies with isolated mitochondria indicate that a limitation of intra-cellular δ-aminolevulinic acid supply is reflected in mitochondrial composition, not just in numbers of organelles.     

Genetic manipulation of a latent defect in yeast cytochrome biosynthesis utilizing cytoduction.

The effects of a mit^? mutation, oxi2, and the ρ° mutation on expression of a defective nuclear structural gene for δ-aminolevulinic acid synthase (cyd1) were compared. The technique of cytoduction was used to introduce oxi2 mitochondria into a cyd1ρ° recipient cell, thereby permitting comparison of isonuclear strains. Like ρ°, the oxi2 mutation caused an apparent unmasking of the cytochrome deficiency associated with the cyd1 mutation, provided cells were grown on glucose. When cyd1 strains with ρ⁺, ρ° or oxi2 mitochondrial genotypes were grown on galactose medium, substantial cytochrome formation occurred in each case. It is concluded that the exacerbation of the cyd1-dependent cytochrome deficiency by ρ° or oxi2 mutations depends upon glucose repression. However, derepression resulting from growth on galactose medium does not fully overcome the cyd1 defect, since both cyd1ρ°oxi2 strains require added δ-aminolevulinic acid for maximum cytochrome biosynthesis.     

Evidence for dynamic resource partitioning between two sympatric reef shark species within the British Indian Ocean Territory

Stable-isotope analyses (δ¹³C, δ¹⁵N and δ³⁴S) of multiple tissues (fin, muscle, red blood cells and plasma), revealed ontogenetic shifts in resource use by grey reef sharks Carcharhinus amblyrhynchos and resource partitioning with silvertip sharks Carcharhinus albimarginatus within the British Indian Ocean Territory marine protected area (MPA). Resource partitioning varied temporally, with C. albimarginatus feeding on more pelagic prey during October to January, potentially attributable to an influx of pelagic prey from outside the MPA at that time. Reef sharks may therefore be affected by processes outside an MPA, even if the sharks do not leave the MPA.     

流溪河水库颗粒有机物及浮游动物碳、氮稳定同位素特征

为了解影响流溪河水库颗粒有机物(POM)碳和氮稳定同位素(δ¹³C和δ¹⁵N)变化的主要因素,及其与浮游动物δ¹³C和δ¹⁵N之间的关系,于2008年5月至12月份对POM及浮游动物的δ¹³C和δ¹⁵N进行了研究。颗粒有机物碳稳定同位素(δ¹³C_POM)和氮稳定同位素(δ¹⁵N_POM)的季节性变化幅度分别为5.1‰和2.2‰,5月和7月份δ¹³C_POM较高,而在10月和12月份降低,这主要与降雨将大量外源有机物带入水库而引起的外源及内源有机物在POM组成上发生变化有关。δ¹⁵N_POM总体呈上升趋势,可能是由降雨引起的外源负荷、初级生产力、生物固氮等因素共同作用的结果。浮游动物的δ¹³C及δ¹⁵N总的变化趋势与POM的相似,也具有明显的季节性变化,食物来源的季节变化可能是造成其变化的主要原因。在5月份,浮游动物的食物来源为POM中δ¹³C较高的部分,也就是外源有机物,而在10月及12月份,其食物则可能主要为浮游植物。     

Stable isotopes reveal contrasting trophic dynamics between host–parasite relationships: A case study of Atlantic salmon (Salmo salar) and parasitic lice (Lepeophtheirus salmonis and Argulus foliaceus)

Across existing fish host–parasite literature, endoparasites were depleted in δ¹⁵N compared to their hosts, while ectoparasitic values demonstrated enrichment, depletion and equivalence relative to their hosts. δ¹³C enrichment varied extensively for both endo- and ectoparasites across taxa and host tissues. In our case study, sea lice (Lepeophtheirus salmonis) were enriched in δ¹⁵N relative to their farmed Atlantic salmon (Salmo salar) hosts, although the value contradicted the average that is currently assumed across the animal kingdom. Common fish lice (Argulus foliaceus) did not show a consistent trend in δ¹⁵N compared to their wild S. salar hosts. Both parasitic species had a range of δ¹³C enrichment patterns relative to their hosts. Farmed and wild S. salar had contrasting δ¹³C and δ¹⁵N, and signals varied across muscle, fin and skin within both groups. L. salmonis and A. foliaceus subsequently had unique δ¹³C and δ¹⁵N, and L. salmonis from opposite US coasts differed in δ¹⁵N. Given the range of enrichment patterns that were exhibited across the literature and in our study system, trophic dynamics from host to parasite do not conform to traditional prey to predator standards. Furthermore, there does not appear to be a universal enrichment pathway for δ¹³C nor δ¹⁵N in parasitic relationships, which emphasizes the need to investigate host–parasite linkages across species.     

Importance of multi-dimensional analyses of resource partitioning in highly mobile species assemblages

Resource partitioning is an essential mechanism enabling species coexistence. The resources that are used by an animal are linked to its morphology and ecology. Therefore, similar species should use similar resources. The ecological niche of an individual summarizes all used resources and is therefore composed of several dimensions. Many methods are established to study different dimensions of an animal's niche. The aim of this study was to demonstrate that a combination of suitable methods is needed to study spatial and dietary resource partitioning of sympatric species in detail. We hypothesized that, while each individual method might identify differences between species, the combined results of several methods will lead to a more complete picture of spatial and dietary resource partitioning. As model organisms we chose the sympatric insectivorous bat species Myotis bechsteinii, M. nattereri, and P. auritus. We examined horizontal habitat use by telemetry, vertical habitat use by measuring δ¹³C, trophic position by measuring δ¹⁵N in wing membrane, and diet composition by molecular fecal analysis. Our results show that each method is able to provide information about spatial/dietary resource partitioning. However, considering further dimensions by combining several methods allows a more comprehensive assessment of dietary and spatial resource partitioning in bats.     

应用稳定同位素研究广西东方洞食物网结构和营养级关系

稳定性同位素技术已经成为研究生态系统食物网结构和营养级关系及其动态变化的重要手段。应用稳定同位素技术(δ13C和δ15N)研究了东风洞的食物网结构和营养级关系。研究结果表明,东风洞主要为腐食食物链,由于在洞穴内黑暗带中无光照也无植物生长,所以碳源主要为东风洞中的土壤有机质,作为第一营养级;主要摄食关系为马陆与土壤有机物质,螺类与土壤有机物质等;在该洞生态系统中,将3种马陆直接作为初级消费者,以隅蛛和其它马陆平均值之间的差值(2.04‰)作为东风洞食物网稳定氮同位素的富集因子。根据营养级模型可知,马陆类群、细长钻螺等土壤动物,裸灶螽和涂闪夜蛾形成第二营养级,即初级消费者;第三营养级包括蜘蛛类、盲蛛、地蜈蚣以及黑眶蟾蜍,为次级消费者。     

Δ5-Dehydroskytanthin und 8-skytanthin in Tecoma stans

The structures of two new alkaioids extracted from Tecoma stans were determined by IR, NMR, MS and m.ps of their picrates and methoiodides. The compounds were characterized as Δ⁵ -dehydroskytanthine and δ-skytanthine.     

Review on biopesticide production by Bacillus thuringiensis subsp. kurstaki since 1990: Focus on bioprocess parameters

Irrespective use of chemical pesticides has led, over the last decades, to several problems such as soil, water and food sources pollution, and generation of a selective pressure causing the emergence of pest resistance. Consequently, researchers have been focusing more on the use of biological control as an alternative strategy. Bacillus thuringiensis (Bt) is one of the most widely studied bacteria in industrial biotechnology and commercialized as an environmentally sustainable biopesticide. Therefore, a huge interest has been allocated for research on this bacterium and several scientific studies have been published on the issue. In this review, we tried to evaluate the scientific production over the last thirty years, for the first time, in terms of number and geographical origin, focusing particularly on B. thuringiensis kurstaki (Btk). It is worth emphasizing that the Btk process engineering involving factors affecting growth, sporulation and toxin formation yields by Bt has not been fully investigated in previous reviews. To this end, the second section of this review provided an updated survey about these conditions, such as nutritional requirements, culture media and fermentation technologies. Relevant information was collected in comparative tables that could be very useful for the scientific community interested in Btk-based biopesticides.     

Effects of the early stage of decomposition on change in carbon and nitrogen isotopes in Sphagnum litter

Abstract

Isotope and elemental composition of carbon (C) and nitrogen (N) as well as its mass loss were measured for Sphagnum fuscum litter after one and two years of incubation in three different soil zones defined by the position of water table in a pristine Sphagnum-dominated peatland on the coast of western Canada. Mass losses were greater for the first year than for the second year, and the greatest loss was found in the oxic zone closest to the peatland surface. Early stage of decomposition clearly affected isotope signatures in Sphagnum litter. Litter δ¹³C values significantly decreased after the first year of incubation. The depletion of ¹³C content during the first year might be related to the loss of more isotopically enriched soluble constituents coupled with the large mass loss. Litter δ¹⁵N values significantly increased after the first year of incubation in spite of the large mass loss. Litters incubated in the oxic zone had the greatest mass loss and ¹⁵N enrichment, suggesting that the enrichment was the result of interactions with soil microbes and preferential loss of lighter N. Conversely, litters incubated in the anoxic zone had smaller mass loss and the amount of N significantly increased, suggesting that the incorporation of bacterial biomass might also contribute to the ¹⁵N enrichment. The ¹⁵N enrichment trend continued in the second year, but the change was not significant as the first year. Increases in the δ¹⁵N values with depth in the near surface Sphagnum peat core suggests that the enrichment trend of litter ¹⁵N abundance with age is likely to continue for much longer periods than observed over the two-year period of this study.