Quantification and analysis of metabolic characteristics of aerobic succinate-producing Escherichia coli under different aeration conditions

The production of succinate by engineered Escherichia coli strains has been widely investigated. In this study, quantitative comparison of metabolic fluxes was carried out for the wild-type E. coli strain and a quintuple mutant strain QZ1111 that was designed for the production of succinate aerobically by knocking out five genes (ptsG, poxB, pta, sdhA, iclR) of the wild-type E. coli MG1655. Metabolic flux distributions of both strains were quantified by ¹³C-labeling experiments, together with the determination of physiological parameters and the expression level of key genes. The experimental results indicated that under the same aeration condition the fraction of oxaloacetate molecules originating from phosphoenolpyruvate was increased in E. coli QZ1111 compared to that in the wild-type E. coli MG1655. The glyoxylate shunt was likely activated in E. coli QZ1111 only under high aeration condition but repressed in other conditions, indicating that the deletion of the iclR gene could not completely remove the repression of the glyoxylate shunt with limited oxygen supply. Our results also suggested further genetic manipulation strategies to enhance the production yield of succinate.     

Regulation of Hippo signaling by metabolic pathways in cancer

Hippo signaling is known to maintain balance between cell proliferation and apoptosis via tight regulation of factors, such as metabolic cues, cell-cell contact, and mechanical cues. Cells directly recognize glucose, lipids, and other metabolic cues and integrate multiple signaling pathways, including Hippo signaling, to adjust their proliferation and apoptosis depending on nutrient conditions. Therefore, the dysregulation of the Hippo signaling pathway can promote tumor initiation and progression. Alteration in metabolic cues is considered a major factor affecting the risk of cancer formation and progression. It has recently been shown that the dysregulation of the Hippo signaling pathway, through diverse routes activated by metabolic cues, can lead to cancer with a poor prognosis. In addition, unique crosstalk between metabolic pathways and Hippo signaling pathways can inhibit the effect of anticancer drugs and promote drug resistance. In this review, we describe an integrated perspective of the relationship between the Hippo signaling pathway and metabolic signals in the context of cancer. We also characterize the mechanisms involved in changes in metabolism that are linked to the Hippo signaling pathway in the cancer microenvironment and propose several novel targets for anticancer drug treatment.     

TheCaesalpinia peltophoroides cell cycle under different aeration conditions

Summary Cell cycle parameters were studied inCaesalpinia peltophoroides meristems proliferating under different oxygen tensions. This species has been selected for mixed planting in degraded areas in Brazil, some of which are occasionally flooded. As the species’ adaptation to oxygen deprivation during flooding is not fully understood, the objective of this study was to characterize the meristematic activity of root cells under various oxygen regimes. Synchronous binucleate cells, induced by a pulse of caffeine, showed a cell-cycle time constant under both control (5.6 mg of O₂ per l) and oxygenated conditions (7.9 and 3.2 mg of O₂ per l). The whole cell cycle lasted 10 h, although the relative duration of metaphase and anaphase/early telophase increased in more hypoxic conditions. The species appeared to utilise oxygen diffusing from the shoot to the root system to maintain cell division and root growth.     

Regulation of respiration in plants: a role for alternative metabolic pathways

Respiratory metabolism includes the reactions of glycolysis, the tricarboxylic acid cycle and the mitochondrial electron transport chain, but is also directly linked with many other metabolic pathways such as protein and lipid biosynthesis and photosynthesis via photorespiration. Furthermore, any change in respiratory activity can impact the redox status of the cell and the production of reactive oxygen species. In this review, it is discussed how respiration is regulated and what alternative pathways are known that increase the metabolic flexibility of this vital metabolic process. By looking at the adaptive responses of respiration to hypoxia or changes in the oxygen availability of a cell, the integration of regulatory responses of various pathways is illustrated.     

Cryopreservation ofTetraselmis suecica cultured under different nutrients regimes

The commercially important member of the PrasinophyceaeTetraselmis suecica CCAP 66/4, which is widely used in the aquaculture industry, can be cryopreserved with levels of post-thaw viability in excess of 65%. The nutritional mode which the alga uses appears to be of secondary importance to the cryoprotectant and cooling protocol used, to maximise survival. Glycerol was the least cytotoxic and most protective of the cryoprotectants employed and a cooling rate of 5 °C min^-1 to -30 °C with a 10-minute equilibration, followed by plunging into liquid nitrogen was found to give the highest levels of post-thaw viability.     

Phylogenetic structure of Brazilian savannas under different fire regimes

Questions: Fire is a strong filter in fire‐prone communities and is expected to assemble closely related species when functional traits are conserved in plant lineages. Do frequent fires assemble savannas with closely related species (phylogenetic clustering)? If so, what are the clades pruned by fire in the phylogenetic trees? Are species of semi‐deciduous seasonal forests, where fires are not frequent, less related than expected by chance (phylogenetic over‐dispersion)? Are life forms conserved in the phylogeny of the species? Location: Central and SE Brazilian savannas (Emas National Park, 18°18′S, 52°54′W; Brasília, 15°56′–15°57′S, 47°53′–47°56′W and Corumbataí‐Itirapina, 22°13′–22°15′S, 47°37′–47°39′W); and close semi‐deciduous seasonal forests (in Pirenópolis, 15°45′S, 49°04′W; Brasília, 15°33′S, 47°51′W; and São Carlos, 21°55′S, 47°48′W). Methods: We recorded woody species in savannas under different fire regimes and in semi‐deciduous seasonal forests. We obtained data from the literature and from field sampling. We compared mean phylogenetic distance of species of savanna and of nearby semi‐deciduous seasonal forest sites. We obtained significance by randomizing the species among the tips of phylogenetic trees. We also assessed whether life forms were evolutionary conserved across phylogeny of the studied plants (phylogenetic signal) with tests based on the variance of phylogenetic independent contrasts. Results: Some sites of savanna under high fire frequency were characterized by phylogenetic over‐dispersion of woody species whereas, in contrast, some sites of semi‐deciduous seasonal forest were characterized by phylogenetic clustering. We found phylogenetic signals in the traits across the phylogeny of the 801 species investigated. Conclusion: Fire may have different roles in assembling plant species in Brazilian savannas than in other fire‐prone communities. We postulate that the absence of phylogenetic clustering in the cerrado is mainly due to the persistence of long‐lived resprouting species from different plant lineages.     

Dynamics of pollen tube growth under different competition regimes

Pollen tube dynamics following different competition regimes were studied in sweet cherry (Prunus avium L.). In the process from pollination to fertilization, a constant reduction in the number of pollen tubes that travel along the style is observed. There could be two main causes of this reduction. One is a physical or physiological constraint consisting of the progressive decrease in the reserves and space available for pollen tube growth along the transmitting tissue of the style, and the other is genetic interaction both among the male gametophytes and between the male gametophytes and the female tissues of the flower. To evaluate the roles that these two forces play in reducing the number of pollen tubes that travel along the style, pistils were subjected to various pollen competition regimes by applying different mixtures of live and dead pollen onto the stigmata. The results obtained were similar when the experiment was repeated with different genotypes over 2 years, both in the laboratory and in the field. The role of stylar constriction is important, but it is not the only cause of pollen tube attrition because with low pollen loads fewer pollen tubes reach the different parts of the style than could fit therein. The fact that under different pollen competition regimes the number of pollen tubes is reduced by the same proportion in each stylar level indicates that genetic interactions play an important role in the control of pollen tube attrition.     

Cultivar variation in cotton photosynthetic performance under different temperature regimes

Cotton (Gossypium hirsutum L.) yields are impacted by overall photosynthetic production. Factors that influence crop photosynthesis are the plants genetic makeup and the environmental conditions. This study investigated cultivar variation in photosynthesis in the field conditions under both ambient and higher temperature. Six diverse cotton cultivars were grown in the field at Stoneville, MS under both an ambient and a high temperature regime during the 2006–2008 growing seasons. Mid-season leaf net photosynthetic rates (P_N) and dark-adapted chlorophyll fluorescence variable to maximal ratios (F_v/F_m) were determined on two leaves per plot. Temperature regimes did not have a significant effect on either P_N or F_v/F_m. In 2006, however, there was a significant cultivar × temperature interaction for P_N caused by PeeDee 3 having a lower P_N under the high temperature regime. Other cultivars’ P_N were not affected by temperature. FM 800BR cultivar consistently had a higher P_N across the years of the study. Despite demonstrating a higher leaf F_v/F_m, ST 5599BR exhibited a lower P_N than the other cultivars. Although genetic variability was detected in photosynthesis and heat tolerance, the differences found were probably too small and inconsistent to be useful for a breeding program.     

Morphological analysis of herbaceous communities under different grazing regimes

Abstract. A methodology for the morphological analysis of herbaceous communities is presented, together with an example of its application in montane grasslands in the province of Córdoba (Argentina) subject to grazing and burning. The method, based on multivariate ordination and classification techniques, enabled the detection of morphological changes at three levels in response to disturbance: (a) characterization of the spatial structure of the vegetation; (b) identification of morphological plant groups; and (c) quantification of morphological shifts among different individuals of a single species. The architecture of the vegetation changed toward a progressive miniaturization of photosynthetic structures and concentration of biomass close to the ground, as disturbance intensity increased. Six morphological plant groups (modes of response) showing different behaviour in relation to competition for light and pressure from large herbivores were identified. Some species, highly preferred by ungulate grazers, showed high morphological variability among morphs growing in different grazing situations, whereas some others were morphologically uniform.     

1,3-Propanediol production by Klebsiella pneumoniae under different aeration strategies

1,3-Propanediol production by Klebsiella pneumoniae was studied in batch cultures under N2 flow and four airflow systems. Different byproducts were formed under different aeration conditions. An anaerobic/aerobic combined fed-batch culture was developed giving 70 g 1,3-propanediol l(-1) and 16 g 2,3-butanediol l(-1) with total diol yield of 0.6 mol(-1) glycerol.     

Chitosan induces different L-arginine metabolic pathways in resting and inflammatory macrophages

Chitosan is a linear polymer of N-acetyl-D-glucosamine and deacetylated glucosamine widely used as a wound-healing accelerator in clinical and veterinary medicine. Chitosan enhances the functions of inflammatory cells such as macrophages (Mphi), inducing the production of cytokines as well as the expression of activation markers, Fc receptors and mannose receptor. In this work we studied the effects of chitosan on the arginine metabolic pathways of both resident and inflammatory (proteose-peptone elicited) rat Mphi. Our results show that low molecular weight (LMW) chitosan activated moderately both the inducible nitric oxide synthase (iNOS) and arginase pathways in resident Mphi. In inflammatory Mphi treated with chitosan instead, the arginase activity was strongly enhanced. Supernatants of chitosan-stimulated Mphi enhanced the proliferation of the rat cell line C6. These findings suggest that the healing activity of chitosan could rely on the enhanced arginase activity observed in a wound-associated inflammatory milieu.     

Consistency of captive giraffe behavior under two different management regimes

Long‐term animal behavior studies are sometimes conducted at a single site, leading to questions about whether effects are limited to animals in the same environment. Our ability to make general conclusions about behavior is improved when we can identify behaviors that are consistent across a range of environments. To extend Veasey and colleagues' ([1996b] Anim Welf 5:139–153) study, I compared not only activity budgets but also social behavior of an all‐female group of giraffe at The Maryland Zoo in Baltimore (MZiB) to those previously observed in breeding groups at The San Diego Zoo's Wild Animal Park (SDZWAP; Bashaw et al. [2007] J Comp Psychol 121:46–53). Morning activity budgets and the maintenance of social relationships were consistent across groups. MZiB female giraffe interacted more frequently and the identity of animals that formed the strongest relationships was less predictable than at SDZWAP. Results support earlier findings that captive giraffe maintain social relationships and suggest that studies of giraffe social relationships and activity are generalizable across a range of captive conditions. Zoo Biol 30:371–378, 2011. © 2010 Wiley‐Liss, Inc.     

不同光环境对红松幼苗光合生理特征的影响

应用Li-6400P便携式光合测定系统于生长季（8月）测定了4种模拟光环境（100%、60%、30%和15%自然光强,分别记为FI、II、LI和WI）和3个实际光环境（林窗、林下和林缘,分别记为G、U和E）下3个苗龄红松（Pinus koraiensis）针叶气体交换参数和净光合速率（P_n）的日变化,以及单位叶面积叶绿素（Chl）含量和比叶质量（LMA）的变化。结果表明:3年和5年生红松在II和LI处理间的P_n基本一致,且均高于FI的P_n;7年生红松在FI处理下的P_n高于其他处理的P_n,各处理的P_n峰值均出现在13:00。3年和5年生红松在LI处理下的最大光合速率（A_max）和暗呼吸速率（R_d）均高于全光FI处理。随光强降低,LMA呈下降趋势,说明红松通过改变LMA的方式适应光环境的变化。3年和5年生红松II处理与G处理间的光合生理指标差异不显著(P>0.05）,LI和WI处理与E处理间同样如此,说明光环境模拟很好地反映了实际的光环境。通过对红松针叶生理生态指标的可塑性分析,得出3种不同苗龄红松可塑性的大小顺序为3年>5年>7年。表明随树龄增大,红松的需光性增加;3年和5年生红松在全光30%～60%条件下生长较好,7年生红松则是在全光下生长最好。     

Antioxidant response of Chlamydomonas reinhardtii grown under different element regimes

Nutrient stress is one of the most favorable ways of increasing neutral lipid and high value‐added output production by microalgae. However, little is known about the level of the oxidative damage caused by nutrient stress for obtaining an optimal stress level for maximum production of specific molecules. In this study, the antioxidant response of Chlamydomonas reinhardtii grown under element deprivation (nitrogen, sulfur, phosphorus and magnesium) and supplementation (nitrogen and zinc) was investigated. All element regimes caused a decrease in growth, which was most pronounced under N deprivation. Element deprivation and Zn supplementation caused significant increases in H₂O₂ and lipid peroxidation levels of C. reinhardtii. Decrease in total chlorophyll level was followed by an increase of total carotenoid levels in C. reinhardtii under N and S deprivation while both increased under N supplementation. Confocal imaging of live cells revealed dramatic changes of cell shape and production of neutral lipid bodies accompanied by a decrease of chlorophyll clusters. Antioxidant capacity of cells decreased under N, S and P deprivation while it increased under N and Zn supplementation. Fluctuation of antioxidant enzyme activities in C. reinhardtii grown under different element regimes refers to different metabolic sources of reactive oxygen species production triggered by a specific element absence or overabundance.     

Toxicity of nitrapyrin to sunflower under different N nutrition regimes

Summary The purpose of this study was to investigate the phytotoxicity of nitrapyrin 2-chloro-6-(trichloromethyl)pyridine to sunflower (Helianthus annuus L.) under different N regimes and to see if N forms affect the phytotoxicity of nitrapyrin. Sunflower was grown in pot culture for 21 days and was fertilized with (NH₄)₂SO₄, NH₄NO₃ and NaNO₃ to provide 0, 100 and 200 ppm N and with nitrapyrin application of 0 and 20 ppm. All N-treated sunflower plants in all N regimes and regardless of titrapyrin treatment produced more root and shoot dry weights and contained a significantly higher N than untreated check. Nitrapyrin toxicity appeared as a curling of leaf margin and a tendril type of stem growth, the visible toxicity symptoms decreased in the order: (NH₄)₂SO₄>NH₄NO₃>NaNO₃. Furthermore nitrapyrin addition suppressed sunflower growth in each N regime, the suppressing effect being greater with (NH₄)₂SO₄ and NH₄NO₃ than as with NaNO₃. Although, shoot growth from plants receiving nitrapyrin was not significantly affected by any N regime, root growth of nitrapyrin-treated plants was somewhat restricted by NH₄ ⁺−N nutrition relative to NO₃ ⁻−N nutrition.