scholarly journals Phosphate availability affects fixed nitrogen transfer from diazotrophs to their epibionts

2019 ◽  
Vol 13 (11) ◽  
pp. 2701-2713 ◽  
Author(s):  
Niels J. Schoffelen ◽  
Wiebke Mohr ◽  
Timothy G. Ferdelman ◽  
Julia Duerschlag ◽  
Sten Littmann ◽  
...  
Keyword(s):  
Nitrogen Transfer ◽  
Fixed Nitrogen ◽  
Phosphate Availability

Researching nitrogen solubility in nitrogen-containing austenitic steels at melting and recrystallization by CALPHAD method

2019 ◽  
pp. 53-66 ◽  
Author(s):  
L. A. Smirnov ◽  
I. I. Gorbachev ◽  
V. V. Popov ◽  
A. Yu. Pasynkov ◽  
A. S. Oryshchenko ◽  
...  
Keyword(s):  
Global Minimum ◽  
Nitrogen Solubility ◽  
Thermodynamic Description ◽  
Solidus Temperature ◽  
Liquidus Line ◽  
Calphad Method ◽  
Austenitic Steels ◽  
Nitrogen Transfer ◽  
Fixed Nitrogen ◽  
System Phase

The CALPHAD method has been employed to compose thermodynamic description of the Fe–Cr–Mn–Ni–Si–C–N system. Using an algorithm based on finding a global minimum of Gibbs energy, the calculations of system phase composition were performed in the temperature range from 1750°C to hardening and in the range of compositions corresponding to 04Kh20N6G11M2AFB steel. Calculations showed that at temperatures above liquidus line, Cr and Mn increase nitrogen solubility in the melt, while Ni and Si reduce it. With an increase in the content of Cr, Mn, Ni, and Si in steel in the studied composition range, both liquidus and solidus temperature decrease. The degree of influence on these temperatures of Cr, Mn, Ni and Si within the steel grade is different and ranges from ~3 to ~14°C. Calculations taking into account the possibility of nitrogen transfer between steel and the atmosphere of air showed that the amount of fixed nitrogen in the alloy under study varies, depending on the composition of the steel and temperature, from ~0.3 to ~0.6 wt%. As the temperature decreases from liquidus to solidus, the amount of fixed nitrogen increases, with the exception of those steel compositions when ferrite and not austenite is released from the liquid phase.

Uptake of soil nitrogen by legumes in mixed swards

1977 ◽  
Vol 28 (3) ◽  
pp. 413 ◽  
Author(s):  
I Vallis ◽  
EF Henzell ◽  
TR Evans
Keyword(s):  
Soil Nitrogen ◽  
The Other ◽  
Nitrogen Transfer ◽  
Soil Mineral ◽  
Soil Mineral Nitrogen ◽  
Fixed Nitrogen ◽  
15N Uptake ◽  
Digitaria Decumbens ◽  
Chloris Gayana ◽  
Macroptilium Atropurpureum

The partitioning of uptake of soil nitrogen between legumes and grasses in mown, mixed swards was studied at two sites in south-eastern Queensland. The swards contained either Lotononis bainesii, Desmodium intortum or Trifolium repens with Digitaria decumbens at one site, and either L. bainesii, T. repens, Macroptilium atropurpureum, Vigna luteola or Stylosanthes guyanensis with Chloris gayana at the other site. (15NH4)2SO4 equivalent to c. 0.3 kg nitrogen ha-1 was added every 4 weeks in an attempt to label the soil mineral nitrogen, and the partitioning of 15N uptake between species used as an estimate of the partitioning of uptake of soil nitrogen. Although two of the legumes (L. bainesii and T. repens) obtained 70–100% of the total 15N uptake at some of the spring harvests, when growth of the associated tropical grasses was limited by low temperatures, none of the legumes obtained more than c. 25% of the annual 15N uptake over a 2-year period. Proportional 15N uptake by the legumes was curvilinearly related to the proportion of legume dry matter yield in the mixtures. Annual 15N uptake by the grass-legume mixtures was up to 360% as high as by the grass control. This had only a small effect on estimates of the proportion of legume nitrogen derived from symbiotic fixation, but caused a large discrepancy in isotopic estimates of nitrogen transfer. The proportion of fixed nitrogen in the legumes averaged 94% at one site and 92% at the other, nearly always exceeded 80%, and was independent of legume yield.

scholarly journals Co-occurrence of Fe and P stress in natural populations of the marine diazotroph <i>Trichodesmium</i>

2020 ◽  
Author(s):  
Noelle A. Held ◽  
Eric A. Webb ◽  
Matthew M. McIlvin ◽  
David A. Hutchins ◽  
Natalie R. Cohen ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Physiological State ◽  
Natural Populations ◽  
Protein Biomarkers ◽  
Fixed Nitrogen ◽  
Nutrient Sources ◽  
Marine Microbe ◽  
Phosphate Availability ◽  
Diffusion Rates ◽  
And Diffusion

Abstract. Trichodesmium is a globally important marine microbe that provides fixed nitrogen to otherwise N limited ecosystems. In nature, nitrogen fixation is likely regulated by iron or phosphate availability, but the extent and interaction of these controls is unclear. From metaproteomics analyses using established protein biomarkers for iron and phosphate stress, we found that co-stress is the norm rather than the exception for field Trichodesmium colonies. Counter-intuitively, the nitrogenase enzyme was most abundant under co-stress, consistent with the idea that Trichodesmium has a specific physiological state under nutrient co-stress. Organic nitrogen uptake was observed to occur simultaneously with nitrogen fixation. Quantification of the phosphate ABC transporter PstC combined with a cellular model of nutrient uptake suggested that Trichodesmium is confronted by the biophysical limits of membrane space and diffusion rates for iron and phosphate acquisition. Colony formation may benefit nutrient acquisition from particulate and organic nutrient sources, alleviating these pressures. The results indicate that to predict the behavior of Trichodesmium, we must consider multiple nutrients simultaneously across biogeochemical contexts.

Partitioning of Symbiotically Fixed Nitrogen in Soybeans and Alfalfa 1

Crop Science ◽  
1984 ◽  
Vol 24 (5) ◽  
pp. 986-990 ◽  
Author(s):  
R. A. Henson ◽  
G. H. Heichel
Keyword(s):  
Fixed Nitrogen

scholarly journals Microbial niche differentiation explains nitrite oxidation in marine oxygen minimum zones

2021 ◽  
Author(s):  
Xin Sun ◽  
Claudia Frey ◽  
Emilio Garcia-Robledo ◽  
Amal Jayakumar ◽  
Bess B. Ward
Keyword(s):  
Nitrogen Loss ◽  
Niche Differentiation ◽  
Nitrite Reduction ◽  
Nitrite Oxidation ◽  
Fixed Nitrogen ◽  
Anoxic Waters ◽  
Biogeochemical Models ◽  
Nitrite Oxidizing Bacteria ◽  
Oxygen Addition ◽  
Oxygen Minimum

AbstractNitrite is a pivotal component of the marine nitrogen cycle. The fate of nitrite determines the loss or retention of fixed nitrogen, an essential nutrient for all organisms. Loss occurs via anaerobic nitrite reduction to gases during denitrification and anammox, while retention occurs via nitrite oxidation to nitrate. Nitrite oxidation is usually represented in biogeochemical models by one kinetic parameter and one oxygen threshold, below which nitrite oxidation is set to zero. Here we find that the responses of nitrite oxidation to nitrite and oxygen concentrations vary along a redox gradient in a Pacific Ocean oxygen minimum zone, indicating niche differentiation of nitrite-oxidizing assemblages. Notably, we observe the full inhibition of nitrite oxidation by oxygen addition and nitrite oxidation coupled with nitrogen loss in the absence of oxygen consumption in samples collected from anoxic waters. Nitrite-oxidizing bacteria, including novel clades with high relative abundance in anoxic depths, were also detected in the same samples. Mechanisms corresponding to niche differentiation of nitrite-oxidizing bacteria across the redox gradient are considered. Implementing these mechanisms in biogeochemical models has a significant effect on the estimated fixed nitrogen budget.

Illite-smectites and the influence of burial diagenesis on the geochemical cycling of nitrogen

Clay Minerals ◽  
1998 ◽  
Vol 33 (4) ◽  
pp. 539-546 ◽  
Author(s):  
P. A. Schroeder ◽  
A. A. McLain
Keyword(s):  
Reaction Mechanisms ◽  
Ostwald Ripening ◽  
Precipitation Reaction ◽  
Oil Well ◽  
Burial Diagenesis ◽  
Fixed Nitrogen ◽  
Geochemical Cycling ◽  
Oil Generation ◽  
Fraction Increase ◽  
Changing Rate

AbstractFixed nitrogen in illite-smectites (I-S) has been measured for Miocene shales from a Gulf of Mexico oil well. Fixed N values for the <0.2 µm fraction increase with depth from 150 ppm (1000 m) to a maximum of 360 ppm (3841 m). This increase is coincident with illitization from 41% I in I-S to 75% I in I-S. Below 3841 m, fixed N values decrease to 190 ppm (4116 m) while I-S is maintained with a slight increase from 77 to 82%. The changes in fixed N with increasing illitization are consistent with the notion that illitization proceeds via both transformation and dissolution/ precipitation reaction mechanisms. The trend of decreasing fixed N in illitic I-S is compatible with surface-controlled crystal growth and Ostwald ripening mechanisms for illitization. The trend may also be linked to the timing of maximum NH] release from kerogen maturation during oil generation. The changing rate of NH+4 liberation from organic matter and multiple illitization reaction mechanisms can result in complex N geochemical cycling pathways throughout early diagenesis to metamorphism.

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