scholarly journals Unrecognized controls on microbial functioning in Blue Carbon ecosystems: The role of mineral enzyme stabilization and allochthonous substrate supply

2020 ◽  
Vol 10 (2) ◽  
pp. 998-1011 ◽  
Author(s):  
Peter Mueller ◽  
Dirk Granse ◽  
Stefanie Nolte ◽  
Magdalena Weingartner ◽  
Stefan Hoth ◽  
...  
Keyword(s):  
Blue Carbon ◽  
Enzyme Stabilization ◽  
Substrate Supply

scholarly journals A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO 2

2011 ◽  
Vol 9 (10) ◽  
pp. 552-560 ◽  
Author(s):  
Elizabeth Mcleod ◽  
Gail L Chmura ◽  
Steven Bouillon ◽  
Rodney Salm ◽  
Mats Björk ◽  
...  
Keyword(s):  
Blue Carbon ◽  
Coastal Habitats

Regulatory Role of Blue Carbon in Estuarine Acidification

2021 ◽  
pp. 277-335
Author(s):  
Abhijit Mitra ◽  
Sufia Zaman
Keyword(s):  
Blue Carbon ◽  
Regulatory Role ◽  
Estuarine Acidification

scholarly journals Compartmentalized system with membrane-bound glycerol kinase. Activity and product distribution versus asymmetrical substrate supply

1991 ◽  
Vol 274 (3) ◽  
pp. 819-824 ◽  
Author(s):  
A Girard ◽  
B Merchie ◽  
B Maïsterrena
Keyword(s):  
Enzyme Activity ◽  
Diffusion Layer ◽  
Cumulative Effect ◽  
Product Distribution ◽  
Substrate Supply ◽  
Enzyme Model ◽  
Membrane Bound ◽  
The Asymmetry

An artificial-membrane-bound glycerokinase chosen as a membrane-bound two-substrate-enzyme model has been used to separate two unequal compartments of a specially designed diffusion cell. An interesting feature is the asymmetry of compartments and the existence of a diffusion layer adjacent to only one face of the enzymic membrane. In such a situation the apparent enzyme activity and the product distribution in the system have been studied versus all the possibilities of combination of ATP and glycerol supply. Our approach has lead us to differentiate two different roles played by a diffusion layer adjacent to a permeable enzymic membrane. Depending on the spatial origin of the enzymic substrates (i.e. from which compartment they derive), the diffusion layer can play either the role of a passive additional resistance to that of the membrane or the role of a third compartment in which the reaction product can partially accumulate before splitting on both parts of the membrane. Our results mainly demonstrate that a membrane-bound enzyme activity and the resulting product distribution occurring in a compartmentalized system may be regulated by the cumulative effect due to the asymmetry in volumes of the compartments, the presence of a diffusion layer and the different possibilities of substrate supply. With the topography studied, which is close to that reported for many ‘in vivo’ situations, the product may be diffused lead to vectorial metabolism processes.

scholarly journals Cytosolic, but not matrix, calcium is essential for adjustment of mitochondrial pyruvate supply

2020 ◽  
Vol 295 (14) ◽  
pp. 4383-4397 ◽  
Author(s):  
Marten Szibor ◽  
Zemfira Gizatullina ◽  
Timur Gainutdinov ◽  
Thomas Endres ◽  
Grazyna Debska-Vielhaber ◽  
...  
Keyword(s):  
Oxidation Reaction ◽  
Control Mechanisms ◽  
Mitochondrial Matrix ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Phenotypic Changes ◽  
Substrate Supply ◽  
Health And Disease ◽  
Malate Aspartate Shuttle ◽  
Working Rat Heart

Mitochondrial oxidative phosphorylation (OXPHOS) and cellular workload are tightly balanced by the key cellular regulator, calcium (Ca2+). Current models assume that cytosolic Ca2+ regulates workload and that mitochondrial Ca2+ uptake precedes activation of matrix dehydrogenases, thereby matching OXPHOS substrate supply to ATP demand. Surprisingly, knockout (KO) of the mitochondrial Ca2+ uniporter (MCU) in mice results in only minimal phenotypic changes and does not alter OXPHOS. This implies that adaptive activation of mitochondrial dehydrogenases by intramitochondrial Ca2+ cannot be the exclusive mechanism for OXPHOS control. We hypothesized that cytosolic Ca2+, but not mitochondrial matrix Ca2+, may adapt OXPHOS to workload by adjusting the rate of pyruvate supply from the cytosol to the mitochondria. Here, we studied the role of malate-aspartate shuttle (MAS)-dependent substrate supply in OXPHOS responses to changing Ca2+ concentrations in isolated brain and heart mitochondria, synaptosomes, fibroblasts, and thymocytes from WT and MCU KO mice and the isolated working rat heart. Our results indicate that extramitochondrial Ca2+ controls up to 85% of maximal pyruvate-driven OXPHOS rates, mediated by the activity of the complete MAS, and that intramitochondrial Ca2+ accounts for the remaining 15%. Of note, the complete MAS, as applied here, included besides its classical NADH oxidation reaction the generation of cytosolic pyruvate. Part of this largely neglected mechanism has previously been described as the “mitochondrial gas pedal.” Its implementation into OXPHOS control models integrates seemingly contradictory results and warrants a critical reappraisal of metabolic control mechanisms in health and disease.

scholarly journals Design of the oxygen and substrate pathways. VII. Different structural limits for oxygen and substrate supply to muscle mitochondria.

1996 ◽  
Vol 199 (8) ◽  
pp. 1699-1709
Author(s):  
E R Weibel ◽  
C R Taylor ◽  
J M Weber ◽  
R Vock ◽  
T J Roberts ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Structural Design ◽  
Muscle Metabolism ◽  
Glucose Consumption ◽  
Acid Oxidation ◽  
Upper Limit ◽  
Substrate Supply ◽  
Small Resistance ◽  
O2 Supply

This paper integrates the results of a series of studies on the supply of O2 and substrates for oxidative muscle metabolism and draws conclusions on the role of structural design in partitioning and limiting substrate supply. The studies compared dogs and goats exercising at different intensities and combined physiological, biochemical and morphometric investigations. In both species, the rate of fatty acid oxidation reached an upper limit at low exercise intensities, and only glucose consumption was increased at higher exercise intensities. The supply of both glucose and fatty acids from the capillaries reached maximal rates at low exercise intensities; this limitation is related to the design of the sarcolemma as calculations suggest that the endothelium introduces only a small resistance to substrate flux. From these findings, it appears that the capillaries are designed to satisfy O2 supply up to maximal O2 demand. The increase in substrate supply to the mitochondria at higher exercise intensities is achieved by drawing on intracellular stores of glycogen and lipids. The size of these stores is larger in dogs than in goats, providing the athletic species with twice the fuel reserves. These findings are interpreted on the basis of a network model with fluxes partitioned between direct and indirect pathways and with some structures shared by more than one function. Whereas O2 is supplied through a direct pathway, the supply of both substrates is split temporally to allow, during exercise, immediate fuel supply to the mitochondria from intracellular stores; these are replaced from the vasculature, during periods of rest, to a size commensurate with high rates of combustion. Considering this complexity, we conclude that the results are compatible with the principle of symmorphosis applied to a network structure and that the adjustment of design to functional demand involves different structures for O2 and for substrates.

When “Blue Carbon” turns white: Isotopic evidence of calcification-driven CO2 emissions in a carbonate seagrass meadow

2021 ◽  
Author(s):  
Mary Zeller ◽  
Bryce Van Dam ◽  
Christian Lopes ◽  
Ashley Smyth ◽  
Michael Böttcher ◽  
...  
Keyword(s):  
Seagrass Meadow ◽  
Solid Phase ◽  
Blue Carbon ◽  
Total Alkalinity ◽  
Carbonate Content ◽  
Carbonate Precipitation ◽  
Seagrass Meadows ◽  
Organic Carbon Burial ◽  
Seagrass Density

<p>Seagrasses are often considered important players in the global carbon cycle, due to their role in sequestering and protecting sedimentary organic matter as “Blue Carbon”.  However, in shallow calcifying systems the ultimate role of seagrass meadows as a sink or source of atmospheric CO<sub>2</sub> is complicated by carbonate precipitation and dissolution processes, which produce and consume CO<sub>2</sub>, respectively.  In general, microbial sulfate, iron, and nitrate reduction produce total alkalinity (TA), and the reverse reaction, the re-oxidation of the reduced species, consumes TA. Therefore, net production of TA only occurs when these reduced species are protected from re-oxidation, for example through the burial of FeS<sub>x</sub> or the escape of N<sub>2</sub>.  Seagrasses also affect benthic biogeochemistry by pumping O2 into the rhizosphere, which for example may allow for direct H2S oxidation.</p><p>Our study investigated the role of these factors and processes (seagrass density, sediment biogeochemistry, carbonate precipitation/dissolution, and ultimately air-sea CO<sub>2</sub> exchange), on CO<sub>2</sub> source-sink behavior in a shallow calcifying (carbonate content ~90%) seagrass meadow (Florida Bay, USA), dominated by Thalassia testudinum. We collected sediment cores from high and low seagrass density areas for flow through core incubations (N<sub>2</sub>, O<sub>2</sub>, DI<sup>13</sup>C, sulfide, DO<sup>13</sup>C flux), solid phase chemistry (metals, PO<sup>13</sup>C, Ca<sup>13</sup>C<sup>18</sup>O<sub>3</sub>, AVS: FeS + H<sub>2</sub>S, CRS: FeS<sub>2</sub> + S<sup>0</sup>), and porewater chemistry (major cations, DI<sup>13</sup>C, sulfide, <sup>34</sup>S<sup>18</sup>O<sub>4</sub>). An exciting aspect of this study is that it was conducted inside the footprint of an Eddy Covariance tower (air-sea CO<sub>2</sub> exchange), allowing us to directly link benthic processes with CO<sub>2</sub> sink-source dynamics.</p><p>During the course of our week long study, the seagrass meadow was a consistent source of CO<sub>2</sub> to the atmosphere (610 ± 990 µmol·m<sup>-2</sup>·hr<sup>-1</sup>).  Elevated porewater DIC near 15 cmbsf suggests rhizosphere O<sub>2</sub> induced carbonate dissolution, while consumption of DIC in the top 5-10 cm suggests reprecipitation.  With high seagrass density, enriched δ<sup>13</sup>C<sub>DIC </sub>in the DIC maximum zone (10-25 cm) suggests continual reworking of the carbonates through dissolution/precipitation processes towards more stable PIC, indicating that seagrasses can promote long-term stability of PIC.  We constructed a simple elemental budget, which suggests that net alkalinity consumption by ecosystem calcification explains >95% of the observed CO<sub>2</sub> emissions.  Net alkalinity production through net denitrification (and loss of N<sub>2</sub>) and net sulfate reduction (and subsequent burial of FeS<sub>2</sub> + S<sup>0</sup>), as well as observed organic carbon burial, could only minimally offset ecosystem calcification.   </p>

scholarly journals The Role of the Upper Tidal Estuary in Wetland Blue Carbon Storage and Flux

2018 ◽  
Vol 32 (5) ◽  
pp. 817-839 ◽  
Author(s):  
Ken W. Krauss ◽  
Gregory B. Noe ◽  
Jamie A. Duberstein ◽  
William H. Conner ◽  
Camille L. Stagg ◽  
...  
Keyword(s):  
Carbon Storage ◽  
Blue Carbon ◽  
Tidal Estuary
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