Effects of discrete bioactive microbial volatiles on plants and fungi

Plants live in association with microorganisms, which are well known as a rich source of specialized metabolites, including volatile compounds. The increasing numbers of described plant microbiomes allowed manifold phylogenetic tree deductions, but less emphasis is presently put on the metabolic capacities of plant‐associated microorganisms. With the focus on small volatile metabolites we summarize (i) the knowledge of prominent bacteria of plant microbiomes; (ii) present the state‐of‐the‐art of individual (discrete) microbial organic and inorganic volatiles affecting plants and fungi; and (iii) emphasize the high potential of microbial volatiles in mediating microbe–plant interactions. So far, 94 discrete organic and five inorganic compounds were investigated, most of them trigger alterations of the growth, physiology and defence responses in plants and fungi but little is known about the specific molecular and cellular targets. Large overlaps in emission profiles of the emitters and receivers render specific volatile organic compound‐mediated interactions highly unlikely for most bioactive mVOCs identified so far.     

Selective retention of organic phosphate esters and phosphonates on aluminium oxide

Compounds containing the –PO₃H₂ function, such as monoesters of phosphoric acid and phosphonic acids, specifically bind to aluminium oxide in aqueous solution under experimental conditions where non-phosphorylated compounds are completely desorbed. The bound organic phosphate can be specifically displaced by aqueous solution of inorganic phosphates thus allowing their separation or detection by a technique similar to that of affinity chromatography. The consequences of this finding for phosphate compound biochemistry are discussed.     

Pyrophosphate of high and low energy. Contributions of pH, Ca2+, Mg2+, and water to free energy of hydrolysis

The equilibrium between inorganic pyrophosphate and inorganic orthophosphate was determined at pH values varying between 6.0 and 8.0, in the presence of different concentrations of MgCl2, mixtures of MgCl2 and CaCl2, and different organic solvents. The reactions were catalyzed by yeast inorganic pyrophosphatase. It was found that at 35 degrees C, depending on the conditions used, the observed equilibrium constant of pyrophosphate hydrolysis vary from a value higher than 4 X 10(3) M (delta Goobs more negative than -5.1 kcal/mol) to a value as low as 3 M (delta Goobs -0.7 kcal/mol). The experimental data were used to compute the equilibrium constants of the reactions involving different ionic species. The data presented are interpreted according to the concept that the Keq of hydrolysis of a high energy compound depends on the difference in solvation energy of reactants and products.     

Microalgae as a source of stable isotopically labeled compounds

Microalgae have the ability to convert inorganic compounds into organic compounds. When they are cultured in the presence of stable (non-radioactive) isotopes (i.e.¹³CO₂,¹⁵NO ₃ ^– ,²H₂O) their biomass becomes labeled with the stable isotopes, and a variety of stable isotopically-labeled compounds can be extracted and purified from that biomass.Two applications for stable isotopically-labeled compounds are as cell culture nutrients and as breath test diagnostics. Bacteria that are cultured with labeled nutrients will produce bacterial products that are labeled with stable isotopes. The presence of these isotopes in the bacterial products, along with recent developments in NMR technology, greatly reduces the time and effort required to determine the three-dimensional structure of macromolecules and the interaction of proteins with ligands. As breath test diagnostics, compounds labeled with¹³C are used to measure the metabolism of particular organs and thus diagnose various disease conditions. These tests are based on the principle that a particular compound is metabolized primarily by a single organ, and when that compound is labeled with¹³C, the appearance of¹³CO₂ in exhaled breath provides information about the metabolic activity of the target organ. Tests of this type are simple to perform, non-invasive, and less expensive than many conventional diagnostic procedures.The commercialization of stable isotopically labeled compounds requires that these compounds be produced in a cost-effective manner. Our approach is to identify microalgal overproducers of the desired compounds, maximize the product content of those organisms, and purify the resulting products.     

Incorporation of P and C into Photosynthetic Products of Ankistrodesmus braunii as Affected by X-Rays

The incorporation of ³²P and ¹⁴C into organic compounds by Ankistrodesmus is strongly inhibited by X-rays. In the same phosphorylated compounds ³²P-incorporation apparently is more severely inhibited by X-rays than the ¹⁴C-labelling. The ³²P-incorporation into organic compounds is more strongly inhibited than ³²P-labelling of inorganic phosphate in the cell. The inhibition of ³²P-incorporation into a number of compounds is strikingly uniform. It is concluded that the inhibition of ³²P-incorporation and of ¹⁴C-incorporation into phosphorylated compounds in vivo is due to an uncoupling by X-rays of photophosphorylation as in vitro. The difference in X-ray sensitivity of ¹⁴C- and ³²P-incorporation into one organic phosphorous compound is attributed to a dual action of X-rays on ³²P-incorporation in organic compounds (both via the uncoupling of photophosphorylation) and only a single effect on ¹⁴C-incorporation and ³²P-labelling of inorganic phosphate. The effect of X-rays on ¹⁴C-incorporation into organic compounds included inhibition in most cases but also stimulation as in the case of glycolic acid. These differences may be due to interference in the intercellular regulations following the application of X-rays. The inhibition of ¹⁴C-incorporation in many cases exhibits different behaviour at low (<200 krad) and high doses. These changes are discussed on the assumption that at the lower doses X-rays cause uncoupling of photophosphorylation and at the higher doses an additional inhibition of electron transport.     

Problems in the application of gel filtration to the desalting of organic compounds: retardation of aromatic and heteroaromatic anions by commonly used salts.

On Bio-Gel P-2 columns, certain inorganic salts elute considerably later than nucleotides and other anionic compounds of similar molecular weight when they are run separately. This would suggest that such compounds should be readily desalted by gel filtration. With some salts (e.g., NaCl, KI, KSCN) this is indeed the case. With others, however(K₂HPO₄, CH₃COONa, HCOONH₄), there is complete overlap between the peaks of the salt and the organic compound. Studies with different organic compounds and salts suggest that this entrapment within the salt peak may be due to opposing electrostatic and hydrophobic influences on the mobility of organic anions.     

Surface microlayers on temperate lowland lakes

At the air–water interface material, organisms accumulate and form a thin layer of organic and inorganic material called the surface microlayer (SML). In order to investigate the development, composition, and metabolism of SML on lakes, samples were collected using a screen sampler along with subsurface water (SSW) in an eutrophic and a mesotrophic lake from April to September 2007. Wind, solar irradiance, and lake temperature were followed continuously. Samples were analyzed for organic and inorganic compounds as well as for photosynthesis and respiration. Most compounds were enriched in the SML relative to the SSW. Enrichment was small, however, probably because sampling was performed on nonslick areas. Most compounds correlated closely between the SML and the SSW, confirming the hypothesis that most SML material originates from the bulk water. Correlations were strongest in the eutrophic lake, probably because external sources had a greater effect on SML concentrations in the mesotrophic lake. Enrichment of compounds and metabolic rates in the SML had similar seasonality and dependency of climatic conditions in the two lakes, suggesting common regulating mechanisms of enrichment and production. Enrichment factors of several compounds were higher at low bulk water concentrations, suggesting that atmospheric deposition then contributed relatively more to concentrations in the SML. Increasing temperature significantly decreased SML enrichment of TOC (total organic carbon), related to changes in TOC composition and higher heterotrophic activity, while wind and solar irradiance had no pronounced enrichment effect on any compound. Net photosynthesis was significantly lower in the SML, experiencing photoinhibition in one-third of the samples. In contrast, respiration was much elevated in the SML. Nonetheless, respiration in the SML never contributed by more than 0.3% of water column respiration, but the combination of enhanced degradation rates of organic carbon in the SML and strong interaction with water below suggests that the SML, nonetheless, may play an important role in degradation of refractory organic carbon. Combining these results, we found that the SML of nonslicked areas on lakes are enriched in organic and inorganic pools and constitute a strong heterotrophic environment, albeit of minor importance for whole lake pelagic metabolism. Handling editor: D. Ryder     

Influence of soil organic matter decomposition on arbuscular mycorrhizal fungi in terms of asymbiotic hyphal growth and root colonization

Soil organic matter is known to influence arbuscular mycorrhizal (AM) fungi, but limited information is available on the chemical components in the organic matter causing these effects. We studied the influence of decomposing organic matter (pure cellulose and alfalfa shoot and root material) on AM fungi after 30, 100, and 300 days of decomposition in nonsterile soil with and without addition of mineral N and P. Decomposing organic matter affected maize root length colonized by the AM fungus Glomus claroideum in a similar manner as other plant growth parameters. Colonized root length was slightly increased by both nitrogen and phosphorus application and plant materials, but not by application of cellulose. In vitro hyphal growth of Glomus intraradices was increased by soil extracts from the treatments with all types of organic materials independently of mineral N and P application. Pyrolysis of soil samples from the different decomposition treatments revealed in total 266 recognizable organic compounds and in vitro hyphal growth of G. intraradices in soil extract positively correlated with 33 of these compounds. The strongest correlation was found with 3,4,5-trimethoxybenzoic acid methyl ester. This compound is a typical product of pyrolysis of phenolic compounds produced by angiosperm woody plants, but in our experiment, it was produced mainly from cellulose by some components of the soil microflora. In conclusion, our results indicate that mycelia of AM fungi are influenced by organic matter decomposition both via compounds released during the decomposition process and also by secondary metabolites produced by microorganisms involved in organic matter decomposition.     

Long-term effects of SO2 on plants,SO2 metabolism and regulation of intracellular pH

The impact of SO₂ on the ionic balance of plants and its implications for intracellular pH regulation was studied to find explanations for long-term effects of SO₂. When sulphur, taken up as SO₂ by the shoots of plants, is not assimilated in organic compounds, but stored as sulphate, an equivalent amount of H⁺ is produced. These H⁺ ions are not buffered chemically, but removed by metabolic processes.On the basis of knowledge on metabolic buffering mechanisms a conceptual model is proposed for the removal of shoot-generated H⁺ by (i) OH^- ions, produced in the leaves when sulphate and nitrate are assimilated in organic compounds and/or by (ii) OH^- ions produced by decarboxylation of organic anions (a biochemical pH stat mechanism). The form in which nitrogen is supplied largely determines the potential of the plant to neutralize H⁺ in the leaves during SO₂ uptake by the proposed mechanisms.In field experiments with N₂ fixing Vicia faba L. crops, the increase of sulphate in the shoots of SO₂-exposed plants was equivalent in charge to the decrease of organic anion content, calculated as the difference between inorganic cation content (C) and inorganic anion content (A), indicating that H⁺ ions produced in the leaves following SO₂ uptake were partly removed by OH^- from sulphate reduction and partly by decarboxylation of organic anions.The appearance of chronic SO₂ injury (leaf damage) in the field experiment at the end of the growing period is discussed in relation to the impact of SO₂ on the processes involved in regulation of intracellular pH. It is proposed that the metabolic buffering capacity of leaf cells is related to the rates of sulphate and nitrate reduction and the import rate of organic anions, rather than to the organic anion content in the vacuoles of the leaf cells.     

The Absorption and Utilization of Phosphate by Young Barley Plants: IV. THE INITIAL STAGES OF PHOSPHATE METABOLISM IN ROOTS

Organic phosphorus compounds have been extracted from the rootsof intact plants which have absorbed radioactive phosphate.The distribution of phosphorus between different organic fractionsof the root during a 24-hour absorption period is markedly influencedby the concentration of phosphorus supplied. Less than 1 minute after entry a significant proportion of theabsorbed phosphorus is found to be in organic compounds. Incorporationinto nucleotides is particularly rapid, whereas incorporationinto hexose phosphates occurs more slowly. The pattern of esterificationis influenced by the phosphate status of the plants. 2: 4-dinitrophenol (10^–4M.) reduces the uptake of phosphorusand also the extent of esterification, the latter effect beingdue solely to reduced incorporation into the nucleotide fraction. Although extensive esterification of phosphate occurs in roots,it appears to be transported to the shoot as inorganic phosphateaccompanied by only a small amount of a single organic compound.     

The distribution of organic and mineral components in leaves and stems of Ranunculus fluitans Lam.

The differences in chemical composition of leaves and stems of Ranunculus fluitans Lam. were investigated. Typical distribution of organic and inorganic compounds were generally found not to be influenced by factors as day-time, eutrophication, or age of the weed bed. Starch, sugars, amino acids, and organic acids were at a higher level in the stem, but inorganic cations and anions were accumulated in the leaf. The distribution pattern and the relative contents of individual sugars, acids, and inorganic ions are discussed in detail.     

Changes in cropland topsoil organic carbon with different fertilizations under long-term agro-ecosystem experiments across mainland China

Topsoil soil organic carbon (SOC) data were collected from long-term Chinese agro-ecosystem experiments presented in 76 reports with measurements over 1977 and 2006. The data set comprised 481 observations (135 rice paddies and 346 dry croplands) of SOC under different fertilization schemes at 70 experimental sites (28 rice paddies and 42 dry croplands). The data set covered 16 dominant soil types found in croplands across 23 provinces of mainland China. The fertilization schemes were grouped into six categories: N (inorganic nitrogen fertilizer only), NP (compound inorganic nitrogen and phosphorus fertilizers), NPK (compound inorganic nitrogen, phosphorus and potassium fertilizers), O (organic fertilizers only), OF (combined inorganic/organic fertilization) and Others (other unbalanced fertilizations such as P only, K only, P plus K and N plus K). Relative change in SOC content was analyzed, and rice paddies and dry croplands soils were compared. There was an overall temporal increase in topsoil SOC content, and relative annual change (RAC, g kg⁻¹ yr⁻¹) ranged −0.14–0.60 (0.13 on average) for dry cropland soils and −0.12–0.70 (0.19 on average) for rice paddies. SOC content increase was higher in rice paddies than in dry croplands. SOC increased across experimental sites, but was higher under organic fertilization and combined organic/inorganic fertilizations than chemical fertilizations. SOC increase was higher under balanced chemical fertilizations with compound N, P and K fertilizers than unbalanced fertilizations such as N only, N plus P, and N plus K. The effects of specific rational fertilizations on SOC increase persisted for 15 years in dry croplands and 20 years in rice paddies, although RAC values decreased generally as the experiment duration increased. Therefore, the extension of rational fertilization in China’s croplands may offer a technical option to enhance C sequestration potential and to sustain long-term crop productivity.     

Manure and peat based iron-organo complexes

Earlier studies have shown that some naturally occuring organic materials can be used as an Fe source for plants. The aim of this research was to study enrichment procedures that would result in complex formation in common, low cost organic materials and to determine the maximum attainable Fe enrichment levels.Three organic materials-farmyard manure (FYM), poultry manure (PM) and Huleh Valley peat (PE) were studied for their characteristics as Fe, Mn and Zn carriers for plant uptake. Various enrichment procedures were investigated. These studies have shown that the enrichment level depends on the metal, pH and the water soluble fraction (WSF) of the organic materials. Maximum enrichment levels (at pH=3.5) were measured after the excess of inorganic salts was removed by leaching. These levels were 5.8–6.6% for Fe, 3.0–3.4% for Mn and 6.0–6.3% for Zn. An infrared spectrum of the Fe enriched WSF showed that most of the ligands in the complex formed are polysaccharides or polysaccharide-like compounds.     

Toxicity of organic and inorganic mercury species in differentiated human neurons and human astrocytes

Organic mercury (Hg) species exert their toxicity primarily in the central nervous system. The food relevant Hg species methylmercury (MeHg) has been frequently studied regarding its neurotoxic effects in vitro and in vivo. Neurotoxicity of thiomersal, which is used as a preservative in medical preparations, is to date less characterised. Due to dealkylation of organic Hg or oxidation of elemental Hg, inorganic Hg is present in the brain albeit these species are not able to readily cross the blood brain barrier. This study compared for the first time toxic effects of organic MeHg chloride (MeHgCl) and thiomersal as well as inorganic mercury chloride (HgCl₂) in differentiated human neurons (LUHMES) and human astrocytes (CCF-STTG1). The three Hg species differ in their degree and mechanism of toxicity in those two types of brain cells. Generally, neurons are more susceptible to Hg species induced cytotoxicity as compared to astrocytes. This might be due to the massive cellular mercury uptake in the differentiated neurons. The organic compounds exerted stronger cytotoxic effects as compared to inorganic HgCl₂. In contrast to HgCl₂ exposure, organic Hg compounds seem to induce the apoptotic cascade in neurons following low-level exposure. No indicators for apoptosis were identified for both inorganic and organic mercury species in astrocytes. Our studies clearly demonstrate species-specific toxic mechanisms. A mixed exposure towards all Hg species in the brain can be assumed. Thus, prospectively coexposure studies as well as cocultures of neurons and astrocytes could provide additional information in the investigation of Hg induced neurotoxicity.     

Microbial functionalization of (–)-ambroxide by filamentous fungi

Abstract

Biocatalysis is a very useful tool for organic chemists to functionalize organic compounds under working conditions milder than chemical ones. This methodology has special significance since it can be an easy way to introduce a functional group in a non-reactive carbon, regio- and stereoselectively. In order to look for new compounds with antioxidant activity we report the transformation of the natural substrate (–)-ambroxide using the enzyme potential of pure strains of the filamentous fungi Alternaria alternata and Cunninghamella sp., following a protocol with growing cell cultures, which produced the new compound 1β-hydroxyambroxide and the previously known compound 3β-hydroxyambroxide. After purification their structures were elucidated by spectroscopic methods. These two metabolites are the products of oxidation of ring A of the starting material, without evidence of other compounds with different functionalization. Both compounds were tested for their activity as free radical scavengers in vitro, using the assay of DPPH (1,1-diphenyl-2-picrylhydrazyl) radical trapping. The results demonstrated that hydroxylation of carbons C-1 and C-3 of (–)-ambroxide with β stereochemistry had no effect on biological activity as an antioxidant compared with the starting material and a reference substance.     

Organic phosphate probes of the avian renal phosphate secretory mechanism

Parathyroid hormone (PTH) stimulates net renal inorganic phosphate (Pi) secretion in domestic fowl (Gallus domesticus). Recent evidence indicates that secreted Pi is derived from a highly sequestered, presumably organic, phosphate pool. A modified Sperber technique was used to survey the response of domestic fowl to unilateral renal portal infusions of organic phosphate compounds that had been implicated in previous studies of Pi secretion. None of the organic phosphate compounds produced a significant unilateral Pi secretory effect. It is concluded that these compounds neither directly stimulate Pi secretion in normal or parathyroidectomized birds, nor are they rate-limiting for the Pi secretory mechanism in birds infused with PTH.     

Reliable computational design of biological-inorganic materials to the large nanometer scale using Interface-FF

Abstract

The function of nanomaterials and biomaterials greatly depends on understanding nanoscale recognition mechanisms, crystal growth and surface reactions. The Interface Force Field (IFF) and surface model database are the first collection of transferable parameters for inorganic and organic compounds that can be universally applied to all materials. IFF uses common energy expressions and achieves best accuracy among classical force fields due to rigorous validation of structural and energetic properties of all compounds in comparison to perpetually valid experimental data. This paper summarises key aspects of parameterisation, including atomic charges and transferability of parameters and current coverage. Examples of biomolecular recognition at metal and mineral interfaces, surface reactions of alloys, as well as new models for graphitic materials and pi-conjugated molecules are described. For several metal–organic interfaces, a match in accuracy of computed binding energies between of IFF and DFT results is demonstrated at ten million times lower computational cost. Predictive simulations of biomolecular recognition of peptides on phosphate and silicate surfaces are described as a function of pH. The use of IFF for reactive molecular dynamics is illustrated for the oxidation of Mo₃Si alloys at high temperature, showing the development of specific porous silica protective layers. The introduction of virtual pi electrons in graphite and pi-conjugated molecules enables improvements in property predictions by orders of magnitude. The inclusion of such molecule-internal polarity in IFF can reproduce cation–pi interactions, pi-stacking in graphite, DNA bases, organic semiconductors and the dynamics of aqueous and biological interfaces for the first time.     

Electrode materials used for electrochemical oxidation of organic compounds in wastewater

Electrochemical oxidation (EO) of organic compounds is an outstanding technology capable of oxidizing organic pollutants to simple inorganic compounds such as H₂O and CO₂. Moreover, EO can be attributed to an energy-efficient process, since it requires only insignificant amount of energy in the form of an applied current or a potential to activate the electrodes. There is a vast variety of electrodes used in EO processes for organic compounds degradation. They are noble metal electrodes, such as Pt and Au, boron-doped diamond (BDD) electrodes, mixed metal oxide (MMO), graphite and carbon electrode, etc. In this regard, it becomes difficult to focus on existing electrode properties and characteristics and choose an anode material for a particular application. The aim of this study was to review information on existing anodes used in EO processes, their advantages and disadvantages, performance and application area. Thus far, MMO electrodes along with BDD electrodes are leading materials used in the processes of EO of dyes, pesticides, pharmaceuticals, industrial wastewaters, etc. This is due to their excellent catalytic properties and resistance to both corrosion and dissolution. The catalytic activity of MMO electrodes strongly depends not only on their composition but also on fabrication methods. Thus, a correlation was made between the methods of manufacturing, efficiency and cost in the MMO electrodes. Despite the wide variety of anodes, most of them are either relatively expensive to be used for large volumes of wastewater, or they consist of potentially toxic metals. Moreover, none of them are sufficiently efficient and stable. Therefore, cost-effective, efficient and “green” anodic materials are still under development.     

Die vielen Seiten des Sulfids. Tödlich und doch lebensnotwendig

Hydrogen sulfide is highly toxic, but nevertheless it has several physiological functions. Animals from sulfide containing habitats are able to protect themselves from sulfide poisoning and furthermore use this reduced sulfur compound for ATP production. Life at the deep‐sea hydrothermal vents entirely depends on the oxidation of inorganic substrates, mainly sulfide. In humans sulfide acts as a gaseous signalling molecule. It is produced in many tissues and takes part in a number of important metabolic processes such as the regulation of blood pressure and insulin secretion. Several severe diseases are caused by dysfunctions in sulfur metabolism. Thus, a detailed knowledge of the reactions and effects of hydrogen sulfide is of considerable clinical relevance.     

Bismuth citrate in the quantification of inorganic phosphate and its utility in the determination of membrane-bound phosphatases

This paper describes a rapid and sensitive method to determine inorganic phosphate, even in the presence of labile organic phosphate compounds and large quantities of proteins. The method eliminates the use of sodium arsenite, a highly toxic compound, substituting bismuth citrate for it to stabilize the phosphomolybdic acid complex formed during the interaction of inorganic phosphate and molybdate reduced by ascorbic acid. This method has also been adapted to microplates and has been used to determine the activities of Na/K ATPase and alkaline phosphatase of intestinal basolateral and luminal plasma membranes.