鸭疫里默氏杆菌铁离子代谢机制研究进展

铁离子是大多数细菌生存所必需的一种营养物质,但过多的铁离子会通过芬顿反应产生的活性氧对细菌造成损伤。因此,细菌通过摄取、调控、螯合、外排等机制维持体内铁离子的稳态。鸭疫里默氏杆菌(Riemerella anatipestifer)是一种最新被归类于威克斯菌科里氏杆菌属的革兰氏阴性菌。该菌主要感染禽类,参与该菌的铁离子代谢基因具有特别之处。本文对鸭疫里默氏杆菌铁离子代谢机制研究进展进行了系统总结和阐述,包括该菌的TonB系统、TonB依赖性受体、Fur蛋白及Dps蛋白等在铁离子转运、调控、螯合中的功能,以及以上蛋白在鸭疫里默氏杆菌致病中的作用,以期更全面地理解鸭疫里默氏杆菌铁代谢机制,并为进一步深入研究该菌铁离子代谢提供理论依据和参考。     

Effect of zinc-amended poultry manure and zinc sulphate on the growth and uptake of zinc by corn (Zea mays L.)

Summary A greenhouse experiment conducted to study the effect of different levels of Zn supplied through Zn-amended poultry manure and ZnSO₄ on corn (Zea mays L.) indicated that both the sources significantly increased the dry matter yield and uptake of zinc. The zinc amended poultry manure at all levels of zinc application was more effective than ZnSO₄ in this respect. The percent zinc in corn derived from the fertilizer and percent utilization of applied zinc from the Zn-amended poultry manure was higher than that from ZnSO₄ when applied at equivalent levels.     

Maternal factors affecting teratogenic response: a need for assessment.

A review of current literature suggests that maternal nutritional status can be an important modulator of the developmental toxicity of a number of agents in the environment. While the provision of multivitamin/multimineral supplements during the periconceptional period is often associated with improved pregnancy outcome, it has been difficult to identify specific nutrient deficiencies as causative factors of abnormal development in humans. One explanation for this is that nutrient deficiencies can arise through a number of means in addition to a simple dietary deficit of the nutrient. The hypothesis is proposed that one mechanism contributing to the embryotoxicity of a diverse group of insults is an alteration in the metabolism of select nutrients. Evidence is presented that zinc is one nutrient whose metabolism can be markedly influenced by a variety of insults. One consequence of this alteration can be a reduction in embryonic zinc uptake, the development of embryonic zinc deficiency and abnormal development.     

Zinc,an unexpected integrator of metabolism?

Even when they no longer require the presence of iron, cells use zinc as a divalent cation, involved in a large variety of catalytic and regulatory functions. This metal is so important that it appears that ribosomes are instrumental in its ultimate storage. Here, we summarize a detailed analysis which investigates the way the global cell metabolism is integrated by zinc. This integration results from the zinc-dependent way in which the one-carbon metabolism is always coupled to the translation process, not only via methionine and S-adenosylmethionine, but via the complex set-up of the modification of the position 34 of the anticodon of tRNAs.     

Variations in Zinc Content of Subcellular Fractions from Young and Old Roots, Stems and Leaves of Broad Beans (Vicia faba)

⁶⁵Zn labelled seeds of broad beans (Vicia faba L.) germinated and grown in a complete nutrient solution containing the radioisotope were used to investigate the change in the subcellular distribution of this trace element during subsequent development of the labelled seeds. Homogenates of leaves, stems and roots were fractionated into cell-wall debris, nuclei, chloroplasts, mitochondria, ribosomes and “soluble” fraction. The concentration of the radioisotope in these fractions, expressed as cpm/mg dry weight, was highest in the soluble fraction and in the ribosomes isolated from young tissues. However, as roots and leaves aged, a general decrease in the overall zinc concentration was followed by a similar drop in the concentration of the metal associated with the “soluble” fraction and ribosomes, causing a more or less uniform zinc distribution pattern. On the other hand, there was a general increase in the zinc concentration of the “soluble” and in the particulate fractions of relatively high sedimentation coefficient from older stem samples. Taking also into consideration the dry weight change per unit volume of the tissues under investigation, the relationship between these variations and the metabolism of the plant is discussed.     

The Role of Malate, Oxalate, and Mustard Oil Glucosides in the Evolution of Zinc-Resistance in Herbage Plants

Malate, oxalate and mustard oils were analysed in zinc-resistant and zinc-sensitive ecotypes of Silene cucubalus Wib., Rumex acetosa L., Thlaspi alpestre L. and Agrostis tenuis Sibth. The effect of zinc on the activities of carbonic anhydrase and peroxidase in Siiene cucubalus was tested. Carbonic anhydrase of the zinc-resistant ecotypes was stimulated by addition in vivo of high amounts of zinc. The high activity of peroxidase in the non-zinc-resistant ecotypes after the addition of zinc documented a poisoning of the sensitive plants by zinc. The amount of oxalate differed greatly between ecotypes. There was, however, no direct correlation between zinc-resistance and oxalate. When applying zinc to the nutrient medium, the synthesis of oxalate was inhibited in zinc-sensitive, but stimulated in zinc-resistant ecotypes of Silene cucubalus and Rumex acetosa. In Thlaspi alpestre high concentrations of mustard oil glucosides were found. Zinc-resistant plants produced twice as much glucosides as sensitive ones. A possible role of mustard oils in zinc-resistance is discussed. In the content of malate there were great quantitative differences between zinc-resistant and zinc-sensitive plants. All zinc-resistant ecotypes of all the species contained much higher concentrations in their green organs than the sensitive ones. It is assumed that malate is a major factor in the evolution of zinc-resistance. Malate may act as a complexing agent for zinc within the plasma, whereas oxalate and mustard oils may function as “terminal acceptors” of large amounts of zinc. The role of malate may be extended by a special transport mechanism, by which zinc is eliminated from the plasma into the vacuole.     

Effects of Temperature and Nutrient Supply on Resource Allocation,Photosynthetic Strategy,and Metabolic Rates of Synechococcus sp.

Temperature and nutrient supply are key factors that control phytoplankton ecophysiology, but their role is commonly investigated in isolation. Their combined effect on resource allocation, photosynthetic strategy, and metabolism remains poorly understood. To characterize the photosynthetic strategy and resource allocation under different conditions, we analyzed the responses of a marine cyanobacterium (Synechococcus PCC 7002) to multiple combinations of temperature and nutrient supply. We measured the abundance of proteins involved in the dark (RuBisCO, rbcL) and light (Photosystem II, psbA) photosynthetic reactions, the content of chlorophyll a, carbon and nitrogen, and the rates of photosynthesis, respiration, and growth. We found that rbcL and psbA abundance increased with nutrient supply, whereas a temperature-induced increase in psbA occurred only in nutrient-replete treatments. Low temperature and abundant nutrients caused increased RuBisCO abundance, a pattern we observed also in natural phytoplankton assemblages across a wide latitudinal range. Photosynthesis and respiration increased with temperature only under nutrient-sufficient conditions. These results suggest that nutrient supply exerts a stronger effect than temperature upon both photosynthetic protein abundance and metabolic rates in Synechococcus sp. and that the temperature effect on photosynthetic physiology and metabolism is nutrient dependent. The preferential resource allocation into the light instead of the dark reactions of photosynthesis as temperature rises is likely related to the different temperature dependence of dark-reaction enzymatic rates versus photochemistry. These findings contribute to our understanding of the strategies for photosynthetic energy allocation in phytoplankton inhabiting contrasting environments.     

One-carbon metabolism,folate, zinc and translation

The translation process, central to life, is tightly connected to the one-carbon (1-C) metabolism via a plethora of macromolecule modifications and specific effectors. Using manual genome annotations and putting together a variety of experimental studies, we explore here the possible reasons of this critical interaction, likely to have originated during the earliest steps of the birth of the first cells. Methionine, S-adenosylmethionine and tetrahydrofolate dominate this interaction. Yet, 1-C metabolism is unlikely to be a simple frozen accident of primaeval conditions. Reactive 1-C species (ROCS) are buffered by the translation machinery in a way tightly associated with the metabolism of iron–sulfur clusters, zinc and potassium availability, possibly coupling carbon metabolism to nitrogen metabolism. In this process, the highly modified position 34 of tRNA molecules plays a critical role. Overall, this metabolic integration may serve both as a protection against the deleterious formation of excess carbon under various growth transitions or environmental unbalanced conditions and as a regulator of zinc homeostasis, while regulating input of prosthetic groups into nascent proteins. This knowledge should be taken into account in metabolic engineering.     

Interaction of zinc with other micronutrient cations

Summary Effect of copper on zinc absorption by wheat (Triticum aestivum L. variety WG 357) seedlings and its translocation within the plant was studied in a nutrient solution culture using Zn⁶⁵.Zinc absorption was increased linearly with time within the limits studied (upto 80 minutes). It decreased, however, with increasing concentration of copper in nutrient solution. Plotting of the reciprocals of rates of zinc absorption vs zinc concentration showed that copper concentration in the nutrient solution inhibited zinc absorption, and this inhibition was competitive. Copper decreased only the absorption of zinc but not its translocation from roots to shoots. re]19750219     

Identification of Accessory Genome Regions in Poultry Clostridium perfringens Isolates Carrying the netB Plasmid

Necrotic enteritis (NE) is an economically important disease of poultry caused by certain Clostridium perfringens type A strains. NE pathogenesis involves the NetB toxin, which is encoded on a large conjugative plasmid within a 42-kb pathogenicity locus. Recent multilocus sequence type (MLST) studies have identified two predominant NE-associated clonal groups, suggesting that host genes are also involved in NE pathogenesis. We used microarray comparative genomic hybridization (CGH) to assess the gene content of 54 poultry isolates from birds that were healthy or that suffered from NE. A total of 400 genes were variably present among the poultry isolates and nine nonpoultry strains, many of which had putative functions related to nutrient uptake and metabolism and cell wall and capsule biosynthesis. The variable genes were organized into 142 genomic regions, 49 of which contained genes significantly associated with netB-positive isolates. These regions included three previously identified NE-associated loci as well as several apparent fitness-related loci, such as a carbohydrate ABC transporter, a ferric-iron siderophore uptake system, and an adhesion locus. Additional loci were related to plasmid maintenance. Cluster analysis of the CGH data grouped all of the netB-positive poultry isolates into two major groups, separated according to two prevalent clonal groups based on MLST analysis. This study identifies chromosomal loci associated with netB-positive poultry strains, suggesting that the chromosomal background can confer a selective advantage to NE-causing strains, possibly through mechanisms involving iron acquisition, carbohydrate metabolism, and plasmid maintenance.     

革兰氏阴性菌锌摄取机制及抵抗宿主营养免疫的策略

锌是一种重要的金属元素,不仅充当许多蛋白质和酶的辅因子,还广泛参与糖类、脂质等的代谢过程。锌通常以二价离子的形式存在,在自然界主要分布在植物、土壤和水中,而在生物体内则是分散于肌肉和骨等组织中。对于大多数革兰氏阴性菌而言,锌离子也是其生长过程中必不可少的营养物质。正常情况下,细菌通过ZnuABC和ZIP锌转运系统从宿主体内夺取锌离子,用于体内蛋白质和酶的合成。当过多的锌离子被摄入时,细菌为了避免锌毒性则会启动特定的锌转录调节蛋白,以维持体内外的锌平衡。另一方面,当宿主察觉体内的锌离子被夺取,便会迅速采取锌限制性营养免疫等措施来制止锌离子的进一步流失。为了抵抗宿主的营养免疫,细菌进化出了相应的抵抗策略。较为典型的例子有鲍曼不动杆菌（Acinetobacter baumannii）的锌金属伴侣ZigA,其可在低锌环境中帮助细菌转运锌离子。本文将介绍革兰氏阴性菌锌摄取机制和抵抗宿主营养免疫的典型策略,为控制细菌感染途径和开发相关免疫疫苗等方面提供理论依据。     

Effect of taurine,l-glutamine and l-histidine addition in an amino acid glucose solution on the cellular bioavailability of zinc

Radioactive zinc was used to study the effect of a binary parenteral nutrient solution, composed of amino acids and glucose, on zinc uptake by fibroblasts. The influence of addition of taurine, l-glutamine and of the increase in l-histidine content of the admixture was assessed. The pure mixture was highly toxic for cells and so it was diluted 1/5 in tyrode buffer with 2% albumin. As compared with cells incubated in the buffer containing albumin, zinc absorption was significantly higher (P < 0.05) in the presence of the amino acids of the mixture. Amino acids thus increased bioavailability by displacing zinc bound to albumin. When the histidine concentration in the nutrient medium (4.2 mm) was doubled, inhibition was noted after 30 min of incubation and zinc uptake thereafter remained comparable to that in histidine-free medium. The addition of glutamine (4.2 mm), usually not present in binary mixtures, resulted in significant differences as compared with glutamine-free control medium. Taurine (0.8 mm), led to a constant increase in zinc uptake by fibroblasts as compared with that obtained with taurine-free mixture. However, ultrafiltration showed that taurine was not able to displace zinc from albumin.     

Over-expression of Zip-13 mRNA in kidney and lung during dietary zinc deficiency in Wistar rats

Zinc is an essential nutrient for all organisms, which is involved in the function of numerous key enzymes in metabolism. Two gene families have been identified involved in zinc homeostasis. ZnT transporters reduce intracellular zinc while Zip transporters increase intracellular zinc. Previous studies in our laboratory have shown that Zip-1, ZnT-1, Zip-2 and LIV-1 mRNA are associated with zinc level in established human breast cancer in nude mice model. In this study, six zinc transporters: ZnT-1, ZnT-2, ZnT-4, Zip-1, Zip-8 and Zip-13 were chosen. We aim to determine the relation between zinc transporters and zinc level in kidney and lung of Wistar rats. Eighteen Wistar rats were randomly divided into three groups: normal group, zinc-deficiency group and pair-fed group. After 22 days, the rats were killed and organs samples were taken, then zinc transporters mRNA were detected by RT-PCR. Compared with the normal group, Zip-13 shows an up-regulation (P < 0.05) in zinc-deficiency group both in kidney and lung, and Zip-8 was significantly lower (P < 0.05) in zinc-deficiency group in kidney.     

Concentration and chemical form of dietary zinc shape the porcine colon microbiome,its functional capacity and antibiotic resistance gene repertoire

Despite a well-documented effect of high dietary zinc oxide on the pig intestinal microbiota composition less is it yet known about changes in microbial functional properties or the effect of organic zinc sources. Forty weaning piglets in four groups were fed diets supplemented with 40 or 110 ppm zinc as zinc oxide, 110 ppm as Zn-Lysinate, or 2500 ppm as zinc oxide. Host zinc homeostasis, intestinal zinc fractions, and ileal nutrient digestibility were determined as main nutritional and physiological factors putatively driving colon microbial ecology. Metagenomic sequencing of colon microbiota revealed only clear differences at genus level for the group receiving 2500 ppm zinc oxide. However, a clear group differentiation according to dietary zinc concentration and source was observed at species level. Functional analysis revealed significant differences in genes related to stress response, mineral, and carbohydrate metabolism. Taxonomic and functional gene differences were accompanied with clear effects in microbial metabolite concentration. Finally, a selection of certain antibiotic resistance genes by dietary zinc was observed. This study sheds further light onto the consequences of concentration and chemical form of dietary zinc on microbial ecology measures and the resistome in the porcine colon.Subject terms: Microbiome, Applied microbiology     

The acrodermatitis enteropathica gene ZIP4 encodes a tissue-specific,zinc-regulated zinc transporter in mice

The human ZIP4 gene (SLC39A4) is a candidate for the genetic disorder of zinc metabolism acrodermatitis enteropathica. To understand its role in zinc homeostasis, we examined the function and expression of mouse ZIP4. This gene encodes a well conserved eight-transmembrane protein that can specifically increase the influx of zinc into transfected cells. Expression of this gene is robust in tissues involved in nutrient uptake, such as the intestines and embryonic visceral yolk sac, and is dynamically regulated by zinc. Dietary zinc deficiency causes a marked increase in the accumulation of ZIP4 mRNA in these tissues, whereas injection of zinc or increasing zinc content of the diet rapidly reduces its abundance. Zinc can also regulate the accumulation of ZIP4 protein at the apical surface of enterocytes and visceral endoderm cells. These results provide compelling evidence that ZIP4 is a zinc transporter that plays an important role in zinc homeostasis, a process that is defective in acrodermatitis enteropathica in humans.     

Improving iron, zinc and vitamin A nutrition through plant biotechnology

Recent understanding of plant metabolism has made it possible to increase the iron, zinc and beta-carotene (provitamin A) content in staple foods by both conventional plant breeding and genetic engineering. Improving the micronutrient composition of plant foods may become a sustainable strategy to combat deficiencies in human populations, replacing or complementing other strategies such as food fortification or nutrient supplementation.     

Plasma zinc, copper, leptin, and body composition are associated in elite female judo athletes

This study evaluated levels of plasma zinc, copper, and leptin, body composition, and their relationship in nine elite female judo athletes under two different training conditions. Body composition and biochemical measurements (hematological indexes, plasma zinc, plasma copper, and plasma leptin) were analyzed 24 h after intense training and following a 5-d period without training (no-training). Plasma leptin and plasma zinc increased with no-training. Plasma zinc correlated negatively with percent fat mass (r=−0.62; r=0.05) and positively with plasma leptin (r=0.83; p=0.002) in the no-training condition Plasma copper did not change during the study and correlated positively with plasma leptin (r=0.66; p=0.05) and with percent fat mass (r=0.80; p=0.007) after training. Percent fat mass was associated negatively with plasma zinc (r=−0.62; p=0.05) in the no-training condition. Moreover percent fat mass was negatively associated with the Zn/Cu plasma ratio under both training conditions (r<−0.78, p<0.001). These results are consistent with the possible function of zinc as a lipid-mobilizing factor and of copper as a limiting factor in energy metabolism.     

Leaching of Zinc,Cadmium, and Lead in a Sandy Soil Due to Application of Poultry Litter

Dissolved organic matter in poultry litter could contribute organic ligands to form complexes with heavy metals in soil. The soluble complexes with heavy metals can be transported downward and possibly deteriorate groundwater quality. To better understand metal mobilization by soluble organic ligands in poultry litter, soil columns were employed to investigate the movement of zinc (Zn), cadmium (Cd), and lead (Pb). Uncontaminated soil was amended with Zn, Cd, and Pb at rates of 400, 8, and 200 mg kg ^{? 1} soil, respectively. Glass tubes, 4.9-cm-diameter and 40-cm-long, were packed with either natural or metal-amended soil. The resulting 20-cm-long column of soils had bulk density of about 1.58 g cm ^{? 3} . Columns repacked with natural or amended soil were leached with distilled water, 0.01 M EDTA, 0.01 M CaCl ₂ , or poultry litter extract (PLE) solutions. Low amounts of Zn, Cd, and Pb were leached from natural soil with the solutions. Leaching of Zn, Cd, or Pb was negligible with distilled water. In the metal-amended soil, EDTA solubilized more Zn, Cd, and Pb than CaCl ₂ and PLE. The breakthrough curves of Zn and Pb in the PLE and CaCl ₂ were similar, indicating they have similar ability to displace Zn and Pb from soils. Compared with Zn and Cd the PLE had a small ability to solubilize Pb from metal-amended soil. Thus, the application of poultry litter on metal-contaminated soils might enhance the mobility of Zn and Cd.     

EFFECT OF DIMETHYL SULFOXIDE ON ZINC65 UPTAKE,RESPIRATION, AND RNA AND PROTEIN METABOLISM IN BEAN (PHASEOLUS VULGARIS) TISSUES

The effect of dimethyl sulfoxide (DMSO) on zinc⁶⁵ uptake, respiration, RNA, and protein metabolism in various tissues of two bean (Phaseolus vulgaris L.) cultivars showing differential growth responses to zinc has been studied. At a concentration of 1%, DMSO stimulated zinc uptake in excised roots, stem-callus tissue, leaf disks, and enzymically isolated leaf cells, but did not significantly alter the uptake and incorporation of C¹⁴-uracil into RNA and C¹⁴-methionine into protein, although a slight inhibition was discernible in some tissues. At a higher concentration (10%) DMSO increased Zn⁶⁵ uptake in excise roots incubated for 2 hr; however, at the same concentration, C¹⁴-uracil and C¹⁴-methionine uptake and incorporation were considerably inhibited in all the tissues. Oxygen uptake as measured with Warburg manometers was impaired, and the inhibition showed a time and concentration dependency. The fact that DMSO inhibited respiration and RNA and protein metabolism, while at the same concentration zinc uptake was increased, suggests that zinc uptake in beans is primarily a non-metabolic process. The possible mechanisms of DMSO action are discussed in the light of its reported effects on membrane permeability and cell metabolism.     

Intake and digestion of horned guan Oreophasis derbianus diets measured in three Mexican zoos

We conducted nutritional analyses of diets offered to and ingested by seven pairs of horned guans (Oreophasis derbianus) in three zoos. Digestibility was calculated with individually housed birds (n=1 at each zoo). Diets offered varied widely among institutions, both in ingredients fed as well as in nutrient composition. Feeding selectivity was evident through differences in composition of diets offered vs. consumed, with fruit (bananas, grape, and/or plantain) and avocado (when offered) highly preferred; green leaves, poultry pellets, and other vegetables comprised lesser proportions of the diet. All facilities fed 2–3X more food than consumed, allowing a great degree of choice of preferred items and potentially consumption of nutritionally imbalanced diets—in particular, mineral constituents. Diets were highly digestible; dry matter (DM) digestion coefficients ranged from 70 to ∼90%; protein digestibility varied from 30 to 80%; fat was >90% digestible. Diet composition was compared with known nutritional requirements of domestic avian species, and feeding recommendations discussed. Despite the wide variability in nutrient composition of diets eaten (i.e. protein 6–10% of DM; fat 2–17% of DM), no overt health problems were noted and all pairs had successfully reproduced on these diets. It is suggested that horned guans may have nutrient requirements more similar to those suggested for other frugivorous birds than values determined for poultry as the physiologic model. Comparisons with native food items, as well as more detailed nutrient balance studies, may provide even better guidelines for captive management of this highly endangered species. Zoo Biol 28:319–330, 2009. © 2009 Wiley-Liss, Inc.