Glucosinolate metabolism and its control

Glucosinolates and their associated degradation products have long been recognized for their distinctive benefits to human nutrition and plant defense. Because most of the structural genes of glucosinolate metabolism have been identified and functionally characterized in Arabidopsis thaliana, current research increasingly focuses on questions related to the regulation of glucosinolate synthesis, distribution and degradation as well as to the feasibility of engineering customized glucosinolate profiles. Here, we highlight recent progress in glucosinolate research, with particular emphasis on the biosynthetic pathway and its metabolic relationships to auxin homeostasis. We further discuss emerging insight into the signaling networks and regulatory proteins that control glucosinolate accumulation during plant development and in response to environmental challenge.     

Quantitative approaches to the analysis of the control and regulation of microbial metabolism

Recently, a number of novel ways of considering the control, regulation and thermodynamics of microbial physiology have been developed and applied. We here present an overview of the new concepts involved, of their limitations and of the most recent attempts to deal with those limitations. We conclude that there no longer exist reasons of principle for vagueness in discussions of the control of microbial physiology and energetics. Further, the novel conceptual methods serve to remove part of the discordance between holistic and reductionistic views of microbial physiology.     

Biological control of hog waste odor through stimulated microbial Fe(III) reduction

Odor control and disposal of swine waste have inhibited expansion of swine production facilities throughout the United States. Swine waste odor is associated primarily with high concentrations of volatile fatty acids (VFAs). Here, we demonstrate that stimulated Fe(III) reduction in hog manure can rapidly remove the malodorous compounds and enhance methane production by 200%. As part of these studies, we enumerated the indigenous Fe(III)-reducing population in swine waste and identified members of the family Geobacteraceae as the dominant species. These organisms were present at concentrations as high as 2 x 10(5) cells g(-1). Several pure cultures of Fe(III) reducers, including Geobacter metallireducens, Geobacter humireducens, Geobacter sulfurreducens, Geobacter grbiciae, Geothrix fermentans, and Geovibrio ferrireducens, readily degraded some or all of the malodorous VFAs found in swine manure. In contrast, Shewanella algae did not degrade any of these compounds. We isolated an Fe(III) reducer, Geobacter strain NU, from materials collected from primary swine waste lagoons. This organism degraded all of the malodorous VFAs tested and readily grew in swine waste amended with Fe(III). When raw waste amended with Fe(III) was inoculated with strain NU, the VFA content rapidly decreased, corresponding with an almost complete removal of the odor. In contrast, the raw waste without Fe(III) or strain NU showed a marked increase in VFA content and a rapid pH drop. This study showed that Fe(III) supplementation combined with appropriate bioaugmentation provides a simple, cost-effective approach to deodorize and treat swine waste, removing a significant impediment to the expansion of pork production facilities.     

Quantification of control of microbial metabolism by substrates and enzymes

The control of substrates or enzymes on metabolic processes can be expressed in quantitative terms. Most of the experimental material found in the literature, however, has been obtained under non-standardized conditions, precluding definite conclusions concerning the magnitude of control. A number of representative examples is discussed and it is concluded that a quantitative analysis of the factors that control metabolism is essential for understanding the microbial behaviour.     

Avian metabolism: its control and evolution

This review discussed metabolism in poultry and wild birds with an emphasis on what remains to be elucidated. Circulating concentrations of glucose are much greater in both poultry and wild birds than in mammals which in turn are higher than in reptiles. The basis for this difference is unknown but does not appear to be related to the requirements of flight. Furthermore, birds exhibit a refractoriness to potential adverse effects of very high circulating concentrations of glucose. Again the basis of this is unclear. There is substantial information on the control of metabolism in poultry, although which hormones are exerting physiologic roles remains to be clarified. There is a tacit but unverified assumption that the control mechanisms are the same in wild birds and in poultry. Despite, significant research focus on metabolism in poultry and to a less extent wild birds, there is a dearth of studies determining metabolism in a quantitative manner.     

Electrochemical changes in media due to microbial

Microbial metabolism affected the electrical impedance parameters of a two terminal-measuring cell-containing growth media. The relationship between microbial growth and relative changes in both The capacitive and resistive parts of impedance was examined. Both components of impedance were shown to be indicative of bacterial growth. In low conductivity media the change in the conductance of the media (G_sol) clearly correlated to bacterial growth. In more conductive media the relative changes in G_sol were smaller, and in these media measurements of the changes of polarization capacitance (C_pol) were useful for monitoring bacterial growth.Yeast growth in two media resulted in large changes in C_pol (20–100%) while the changes in G_sol were very small (1–4%). This result indicated that, for some combinations of microorganisms and media, measuring C_pol might be preferable over G_sol for the detection of microbial growth.Microbial metabolism resulted in a change of 2–2.5 units in pH. This pH change resulted in a 40% change in C_pol but less than a 14% change in G_sol.     

Using non-enzymatic chemistry to influence microbial metabolism

1. Download : Download high-res image (154KB)
2. Download : Download full-size image

     

Application of macroscopic principles to microbial metabolism

General expressions for mass, elemental, energy, and entropy balances are derived and applied to microbial growth and product formation. The state of the art of the application of elemental balances to aerobic and heterotrophic growth is reviewed and extended somewhat to include the majority of the cases commonly encountered in biotechnology. The degree of reduction concept is extended to include nitrogen sources other than ammonia. The relationship between a number of accepted measures for the comparison of substrate yields is investigated. The theory is illustrated using a generalized correlation for oxygen yield data. The stoichiometry of anaerobic product formation is briefly treated, a limit to the maximum carbon conservation in product is derived, using the concept of elemental balance. In the treatment of growth energetics the correct statement of the second law of thermodynamics for growing organisms is emphasized. For aerobic heterotrophic growth the concept of thermodynamic efficiency is used to formulate a limit the substrate yield can never surpass. It is combined with a limit due to the fact that the maximum carbon conservation in biomass can obviously never surpass unity. It is shown that growth on substrates of a low degree of reduction is energy limited, for substrates of a high degree of reduction carbon limitation takes over. Based on a literature review concerning yield data some semiempirical notions useful for a preliminary evolution of aerobic heterotrophic growth are developed. The thermodynamic efficiency definition is completed by two other efficiency measures, which allow derivation of simple equations for oxygen consumption and heat production. The range of validity of the constancy of the rate of heat production to the rate of oxygen consumption is analyzed using these efficiency measures. The energetic of anaerobic growth are treated—it is shown that an approximate analysis in terms of an enthalpy balance is not valid for this case, the evaluation of the efficiency of growth has to be based on Gibbs free energy changes. A preliminary analysis shows the existence of regularities concerning the free energy conservation on anaerobic growth. The treatment is extended to include the effect of growth rate by the introduction of a linear relationship for substrate consumption. Aerobic and anaerobic growth are discussed using this relationship. A correlation useful in judging the potentialities for improvement in anaerobic product formation processes is derived. Finally the relevance of macroscopic principles to the modeling of bioengineering systems is discussed.     

Hypoglycosylation due to dolichol metabolism defects

Dolichol phosphate is a lipid carrier embedded in the endoplasmic reticulum (ER) membrane essential for the synthesis of N-glycans, GPI-anchors and protein C- and O-mannosylation. The availability of dolichol phosphate on the cytosolic site of the ER is rate-limiting for N-glycosylation. The abundance of dolichol phosphate is influenced by its de novo synthesis and the recycling of dolichol phosphate from the luminal leaflet to the cytosolic leaflet of the ER. Enzymatic defects affecting the de novo synthesis and the recycling of dolichol phosphate result in glycosylation defects in yeast or cell culture models, and are expected to cause glycosylation disorders in humans termed congenital disorders of glycosylation (CDG). Currently only one disorder affecting the dolichol phosphate metabolism has been described. In CDG-Im, the final step of the de novo synthesis of dolichol phosphate catalyzed by the enzyme dolichol kinase is affected. The defect causes a severe phenotype with death in early infancy. The present review summarizes the biosynthesis of dolichol-phosphate and the recycling pathway with respect to possible defects of the dolichol phosphate metabolism causing glycosylation defects in humans.     

Morbidity, due to schistosomiasis mansoni, and its control in Subsaharan Africa

The measuring and monitoring of morbidity are essential components of schistosomiasis control programmes. Bruno Gryseels and Anton Polderman assess the objectives, difficulties and importance of morbidity control of schistosomiasis mansoni in subsaharan Africa.     

柑橘溃疡病及其微生物防治研究进展

柑橘是我国第一大水果,柑橘溃疡病是导致柑橘产量和品质下降的最具破坏性细菌性病害之一,给柑橘产业造成了巨大的经济损失,严重阻碍了柑橘产业的可持续发展。微生物防治柑橘溃疡病具有安全、环保、高效等优点,是当前研究的热点。本文主要概述了柑橘溃疡病特征及其病原菌分类、分布,全面分析了柑橘溃疡病病原菌主要致病机理和协助致病机理;系统梳理了柑橘溃疡病生防微生物的多样性;重点总结了微生物通过产生活性物质、诱导激活植物免疫防御系统等防治柑橘溃疡病的作用机制;最后,我们提出了柑橘溃疡病微生物防治面临的挑战以及未来可能的解决途径,以期为柑橘产业的健康发展提供参考。     

Regulation of the immune response to cestode infection by progesterone is due to its metabolism to estradiol

The aim of this work was to investigate the role of progesterone during Taenia crassiceps cysticercosis, and the immunological mechanisms involved in its effects, by relating progesterone treatment to whole parasite counts, to host humoral and cellular immune response, to the presence or absence of nuclear receptors to sex steroids in splenocytes, and to serum sex steroid levels in infected mice of both genders. Progesterone treatment increased parasite loads two-fold in females and three-fold in males compared with control mice. The expression of the Th2 cytokine profile (IL-4, IL-6 and IL-10) was markedly increased in infected mice of both genders, while progesterone treatment returned this expression to basal levels. However, the Th1 cytokine profile (IFN-gamma and TNF-alpha) was not affected by infection, whilst progesterone treatment increased the expression of both cytokines two-fold compared to uninfected, infected and placebo-treated mice. Testosterone serum levels decreased in infected male mice by 95%, and treatment with progesterone did not affect them. In females, no change in testosterone levels was observed. Progesterone levels increased three-fold only in progesterone-treated infected mice of both sexes, while estradiol levels in female and male progesterone-treated infected mice increased two-fold compared to infected control mice. The infection markedly induced the expression of progesterone receptor (PR) isoforms A and B in splenocytes of infected mice of both genders (five-fold). Metabolism of progesterone to estradiol was demonstrated by the use of the anti-estrogen tamoxifen, which reduced parasite loads 100% in infected mice of both sexes treated with progesterone. These results suggest that progesterone, possibly through its metabolism to estradiol, affects establishment, growth and reproduction of the helminth parasite T. crassiceps.     

Quantitation of microbial metabolism

Quantitation is a characteristic property of natural sciences and technologies and is the background for all kinetic and dynamic studies of microbial life. This presentation concentrates therefore on materials and methods as tools necessary to accomplish a sound, quantitative and mechanistic understanding of metabolism. Mathematical models are the software, bioreactors, actuators and analytical equipment are the hardware used. Experiments must be designed and performed in accordance with the relaxation times of the biosystem investigated; some of the respective consequences are discussed and commented in detail. Special emphasis is given to the required density, accuracy and reproducibility of data as well as their validation.     

Ontogeny of odor liking during childhood and its relation to language development

One important aspect of odor hedonics is its plasticity during human development. The present study set out to probe the modulators of such olfactory change during that period by testing the hypothesis that language and semantic representations of objects are strong organizers of odor liking. To this end, 15 three-year-old children were tested in a longitudinal study. Participants were exposed to exactly the same 12 odorants once a year over a 3-year period. At each experimental session, they were asked to answer 2 questions: 1) "Do you like or dislike this odor?" and 2) "Can you tell me what it is?" The level of language production was assessed on a standardized test. The 3-year-old children were found to categorize the same number of odorants as liked and as disliked. The follow-up study, in contrast, showed that at 5 years of age they categorized more of these odors as liked and that the shift was significant only in the children with higher language production skills. Taken as a whole, these findings suggest that the 3- to 5-year age range, when children begin to master language, is a turning point in the construction of olfactory hedonic categories during childhood.     

Mammalian iron metabolism and its control by iron regulatory proteins

Cellular iron homeostasis is maintained by iron regulatory proteins 1 and 2 (IRP1 and IRP2). IRPs bind to iron-responsive elements (IREs) located in the untranslated regions of mRNAs encoding protein involved in iron uptake, storage, utilization and export. Over the past decade, significant progress has been made in understanding how IRPs are regulated by iron-dependent and iron-independent mechanisms and the pathological consequences of IRP2 deficiency in mice. The identification of novel IREs involved in diverse cellular pathways has revealed that the IRP-IRE network extends to processes other than iron homeostasis. A mechanistic understanding of IRP regulation will likely yield important insights into the basis of disorders of iron metabolism. This article is part of a Special Issue entitled: Cell Biology of Metals.     

番茄灰霉病害及其微生物防治的研究进展

综述了番茄灰霉病的病害,并从国内外拮抗菌以及内生菌的筛选和利用等方面概述了番茄灰霉病微生物防治的研究进展,提出了目前番茄灰霉病微生物防治的问题及今后的应用前景。