scholarly journals Nitrilotriacetate Stimulation of Anaerobic Fe(III) Respiration by Mobilization of Humic Materials in Soil

2003 ◽  
Vol 69 (9) ◽  
pp. 5255-5262 ◽  
Author(s):  
Y. Luu ◽  
B. A. Ramsay ◽  
J. A. Ramsay
Keyword(s):  
Humic Substances ◽  
Direct Contact ◽  
Enrichment Culture ◽  
Nitrilotriacetic Acid ◽  
Soil Extract ◽  
Alginate Beads ◽  
Electron Shuttling ◽  
Humic Materials ◽  
Dialysis Membranes ◽  
Stimulation Of

ABSTRACT An enrichment culture capable of naphthalene mineralization reduced Fe(III) oxides without direct contact in anaerobic soil microcosms when the Fe(III) was placed in dialysis membranes or entrapped within alginate beads. Both techniques demonstrated that a component in soil, possibly humic materials, facilitated Fe(III) reduction when direct contact between cells and Fe(III) was not possible. The addition of the synthetic Fe(III) chelator, nitrilotriacetic acid (NTA), to soil enhanced Fe(III) reduction across the dialysis membrane and alginate beads, with the medium changing from clear to a dark brown color. An NTA-soil extract was more effective in Fe(III) reduction than the extracted soil itself. Characteristics of the NTA extract were consistent with that of humic substances. The results indicate that NTA improved Fe(III) reduction not by Fe(III) solubilization but by extraction of humic substances from soil into the aqueous medium. This is the first study in which stimulation of Fe(III) reduction through the addition of chemical chelators is shown to be due to the extraction of electron-shuttling compounds from the soil and not to solubilization of the Fe(III) and indicates that mobilization of humic materials could be an important component of anaerobic biostimulation.

scholarly journals Extracellular Electron Transfer to Fe(III) Oxides by the Hyperthermophilic Archaeon Geoglobus ahangari via a Direct Contact Mechanism

2013 ◽  
Vol 79 (15) ◽  
pp. 4694-4700 ◽  
Author(s):  
Michael P. Manzella ◽  
Gemma Reguera ◽  
Kazem Kashefi
Keyword(s):  
Electron Acceptor ◽  
Direct Contact ◽  
Alginate Beads ◽  
Hydrothermal Systems ◽  
Microbial Reduction ◽  
Extracellular Electron Transfer ◽  
Cell Contact ◽  
Content Type ◽  
Chemical Conditions ◽  
Contact Mechanism

ABSTRACTThe microbial reduction of Fe(III) plays an important role in the geochemistry of hydrothermal systems, yet it is poorly understood at the mechanistic level. Here we show that the obligate Fe(III)-reducing archaeonGeoglobus ahangariuses a direct-contact mechanism for the reduction of Fe(III) oxides to magnetite at 85°C. Alleviating the need to directly contact the mineral with the addition of a chelator or the electron shuttle anthraquinone-2,6-disulfonate (AQDS) stimulated Fe(III) reduction. In contrast, entrapment of the oxides within alginate beads to prevent cell contact with the electron acceptor prevented Fe(III) reduction and cell growth unless AQDS was provided. Furthermore, filtered culture supernatant fluids had no effect on Fe(III) reduction, ruling out the secretion of an endogenous mediator too large to permeate the alginate beads. Consistent with a direct contact mechanism, electron micrographs showed cells in intimate association with the Fe(III) mineral particles, which once dissolved revealed abundant curled appendages. The cells also produced several heme-containing proteins. Some of them were detected among proteins sheared from the cell's outer surface and were required for the reduction of insoluble Fe(III) oxides but not for the reduction of the soluble electron acceptor Fe(III) citrate. The results thus support a mechanism in which the cells directly attach and transfer electrons to the Fe(III) oxides using redox-active proteins exposed on the cell surface. This strategy confers onG. ahangaria competitive advantage for accessing and reducing Fe(III) oxides under the extreme physical and chemical conditions of hot ecosystems.

Stimulation of Plant Growth by Humic Substances

1976 ◽  
Vol 40 (6) ◽  
pp. 876-879 ◽  
Author(s):  
Yong Seok Lee ◽  
Richmond J. Bartlett
Keyword(s):  
Plant Growth ◽  
Humic Substances ◽  
Stimulation Of

ORGANIC MATTER CHARACTERISTICS OF UNDISTURBED AND CULTIVATED CHERNOZEMIC AND SOLONETZIC A HORIZONS

1979 ◽  
Vol 59 (4) ◽  
pp. 349-356 ◽  
Author(s):  
J. F. DORMAAR
Keyword(s):  
Organic Matter ◽  
Humic Substances ◽  
Chelating Resin ◽  
Anthropogenic Pressures ◽  
Organic C ◽  
Amide Bonds ◽  
Acid Ratio ◽  
Humic Materials ◽  
Fallow System ◽  
Extractable Organic Matter

Under a wheat-fallow system of farming practised on Brown, Dark Brown, and Black Chernozemic soils, on a Black Solodized Solonetz, and on Brown and Black Solods, organic C decreased by as much as 60%; the humic acid/fulvic acid ratio decreased little for the semiarid soils but up to 38% for the Black soils; ethanol/benzene-extractable organic matter increased by as much as 330%; chelating resin-extractable C increased by 27–115%; and total acidity of the extracted humic substances increased up to 36%. The ash contents of the humic substances from the Ah horizons were all less than 12%, whereas those of the Ap horizons varied between 20 and 28%. Apparent differences between the infrared spectra of the resin-extractable humic substances of the Ah and Ap horizons existed particularly near 2920 and 1550 cm−1 suggesting less aliphatic C-H and amide bonds. Anthropogenic pressures have wrought, therefore, distinct measurable qualitative changes, i.e., the general trend with cultivation was towards humic materials with a decreased proportion of side chain components, such as C-H and NH2 groups, but increased carboxyl group content.

scholarly journals Microbially Mediated Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5- Triazine by Extracellular Electron Shuttling Compounds

2006 ◽  
Vol 72 (9) ◽  
pp. 5933-5941 ◽  
Author(s):  
Man Jae Kwon ◽  
Kevin T. Finneran
Keyword(s):  
Humic Substances ◽  
Electron Donor ◽  
Cell Suspensions ◽  
Electron Shuttle ◽  
Geobacter Metallireducens ◽  
Electron Shuttling ◽  
Resting Cell ◽  
Molar Basis ◽  
Novel Approach

ABSTRACT The potential for humic substances to stimulate the reduction of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was investigated. This study describes a novel approach for the remediation of RDX-contaminated environments using microbially mediated electron shuttling. Incubations without cells demonstrated that reduced AQDS transfers electrons directly to RDX, which was reduced without significant accumulation of the nitroso intermediates. Three times as much reduced AQDS (molar basis) was needed to completely reduce RDX. The rate and extent of RDX reduction differed greatly among electron shuttle/acceptor amendments for resting cell suspensions of Geobacter metallireducens and G. sulfurreducens with acetate as the sole electron donor. AQDS and purified humic substances stimulated the fastest rate of RDX reduction. The nitroso metabolites did not significantly accumulate in the presence of AQDS or humic substances. RDX reduction in the presence of poorly crystalline Fe(III) was relatively slow and metabolites transiently accumulated. However, adding humic substances or AQDS to Fe(III)-containing incubations increased the reduction rates. Cells of G. metallireducens alone reduced RDX; however, the rate of RDX reduction was slow relative to AQDS-amended incubations. These data suggest that extracellular electron shuttle-mediated RDX transformation is not organism specific but rather is catalyzed by multiple Fe(III)- and humic-reducing species. Electron shuttle-mediated RDX reduction may eventually become a rapid and effective cleanup strategy in both Fe(III)-rich and Fe(III)-poor environments.

Effect of food intake on intestinal cholesterol synthesis in rats

1986 ◽  
Vol 251 (3) ◽  
pp. G362-G369
Author(s):  
K. R. Feingold ◽  
G. Zsigmond ◽  
S. R. Lear ◽  
A. H. Moser
Keyword(s):  
Small Intestine ◽  
Food Intake ◽  
Direct Contact ◽  
Cholesterol Synthesis ◽  
Third Trimester ◽  
Increase Food Intake ◽  
Effect Of Food ◽  
Small Intestinal ◽  
Stimulation Of

The mechanism by which diabetes results in an increase in small intestinal cholesterol synthesis is unknown. Previous studies have demonstrated that limiting food intake prevents the increase in intestinal cholesterol synthesis, and it has therefore been proposed that the stimulation of cholesterol synthesis in the small intestine is secondary to the hyperphagia that is associated with poorly controlled diabetes. To shed further light on the role of hyperphagia we have studied the effect on cholesterol synthesis of a variety of conditions that increase food intake. In third-trimester pregnant animals, lactating animals, obese animals, and in animals infused intragastrically with 16 g glucose/day vs. 8 g glucose/day, we have observed that an increase in food intake is associated with an increase in small intestinal cholesterol synthesis. Furthermore, these findings support the hypothesis that hyperphagia is the chief stimulus for the increase in cholesterol synthesis in the small intestine of diabetic animals. Additional studies have demonstrated that simply increasing the bulk of food ingested by adding Alphacel to the diet does not alter cholesterol synthesis in the small intestine. Lastly, in animals in whom Thiry fistulas were surgically constructed we observed that cholesterol synthesis is increased in the diabetic animals in both the segment of the small intestine in contact with the food stream and the segment of the small intestine that is excluded from contact. This observation suggests that the direct contact of the intestinal mucosa with caloric sources is not the sole trigger for increasing small intestinal cholesterol synthesis in hyperphagic diabetic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Soil enrichment for the isolation of sporangial subgroup II Bacillus species, and observations concerning a coil-forming member of this group

1972 ◽  
Vol 18 (7) ◽  
pp. 1031-1038
Author(s):  
R. T. Wood ◽  
L. E. Casida Jr.
Keyword(s):  
Ph Value ◽  
Enrichment Culture ◽  
Divalent Cations ◽  
Soil Extract ◽  
Bacillus Species ◽  
Biochemical Tests ◽  
Soil Medium ◽  
Soil Enrichment ◽  
Subgroup Ii ◽  
Characteristic Features

Enrichment culture procedures are described which allow recovery from soil of mainly sporangial subgroup II Bacillus species, subgroup I plus subgroup II, or the latter plus a coil-forming member of subgroup II. After isolation, the coil-forming type grew normally and sporulated extensively only on agarized soil medium. Growth was normal on soil extract agar but sporulation was less extensive. Limited sporulation occurred when divalent cations were added to more conventional media. Normal vegetative growth occurred on other media investigated only when the pH value was held within relatively narrow limits. The presence of carbohydrate in agar media caused partial growth inhibition, a lack of catalase activity, and the formation of very long coiled cells plus pleomorphic cells, whereas overt cell lysis occurred in vigorously shaken broth cultures. These responses possibly reflect an unbalanced growth condition caused by growth at pH extremes, and not by carbohydrate per se. The characteristic features that set the coil-forming bacilli apart from other subgroup II Bacillus species were shown to be (1) their inability to grow at pH values below 6.5, (2) their inability to ferment carbohydrates, (3) their high oxygen requirement for growth, and (4) their ability to reduce thiosulfate to H2S. In addition, these bacilli can be distinguished from closely related established species by other biochemical tests.

Effect of Humic Substances on Americium (III) Retention onto Silica

1988 ◽  
Vol 127 ◽  
Author(s):  
Valerie Moulin ◽  
Denise Stammose
Keyword(s):  
Ionic Strength ◽  
Humic Substances ◽  
Safety Assessment ◽  
Natural Waters ◽  
Major Influence ◽  
Liquid Interfaces ◽  
Aquifer Systems ◽  
Humic Materials ◽  
Solid Liquid ◽  
Influence Of Ph

ABSTRACTThe migration/retention phenomena of radionuclides in geological systems are of great interest for the safety assessment of a nuclear disposal. Interactions at solid/liquid interfaces play a significant role in the speculation and transport of radionuclides in aquifer systems. Oxide surfaces and humic substances which occur in natural waters in large concentration ranges (from few mg/1 to several hundred mg/1) may have a major influence on radionuclides behaviour. For this purpose, studies have been carried out on a ternary system: oxide-humic substances-americium (III). The influence of pH, ionic strength and humic concentration on the adsorption of americium onto silica has been investigated. The ionic strength of the solution (0.1 and 0.01) has little effect on the americium adsorption. In the presence of humic materials, the fixation of americium is enhanced at low pH (pH<5) whereas, at higher pH (pH>5), the adsorption is lowered and dependent of humic concentration.

Stimulation of Tetrabromobisphenol A Binding to Soil Humic Substances by Birnessite and the Chemical Structure of the Bound Residues

2016 ◽  
Vol 50 (12) ◽  
pp. 6257-6266 ◽  
Author(s):  
Fei Tong ◽  
Xueyuan Gu ◽  
Cheng Gu ◽  
Jinyu Xie ◽  
Xianchuan Xie ◽  
...  
Keyword(s):  
Humic Substances ◽  
Chemical Structure ◽  
Tetrabromobisphenol A ◽  
Bound Residues ◽  
Stimulation Of

Inhibition of iron precipitation by humic substances in field drains

1994 ◽  
Vol 123 (2) ◽  
pp. 247-252 ◽  
Author(s):  
D. Vaughan ◽  
B. G. Ord
Keyword(s):  
Humic Substances ◽  
Oxidation State ◽  
Ferrous Iron ◽  
Fulvic Acids ◽  
Iron Deposition ◽  
Humic And Fulvic Acids ◽  
Iron Precipitation ◽  
Humic Materials ◽  
Drainage Waters

SummaryFerrous iron is oxidized and precipitated as iron ochre in field drains. In drainage waters taken from an ochre-producing site near Aberdeen, Scotland in 1987, iron deposition was inhibited by the addition of humic and fulvic acids, which form complexes with Fe(II). The inhibition was dependent on the concentrations of soluble humic materials and the proportion of Fe complexed. Iron deposition in the presence of humic substances is discussed in relation to the amount of the cation which is complexed and its oxidation state.

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