scholarly journals Bistability in the redox chemistry of sediments and oceans

2020 ◽  
Vol 117 (52) ◽  
pp. 33043-33050
Author(s):  
Sebastiaan J. van de Velde ◽  
Christopher T. Reinhard ◽  
Andy Ridgwell ◽  
Filip J. R. Meysman
Keyword(s):  
Iron Sulfide ◽  
Redox Chemistry ◽  
Small Perturbations ◽  
Evolutionary Transitions ◽  
Positive Feedbacks ◽  
Iron Sulfur ◽  
Iron Sulfide Minerals ◽  
History Of ◽  
Redox Transitions ◽  
Marine Productivity

For most of Earth’s history, the ocean’s interior was pervasively anoxic and showed occasional shifts in ocean redox chemistry between iron-buffered and sulfide-buffered states. These redox transitions are most often explained by large changes in external inputs, such as a strongly altered delivery of iron and sulfate to the ocean, or major shifts in marine productivity. Here, we propose that redox shifts can also arise from small perturbations that are amplified by nonlinear positive feedbacks within the internal iron and sulfur cycling of the ocean. Combining observational evidence with biogeochemical modeling, we show that both sedimentary and aquatic systems display intrinsic iron–sulfur bistability, which is tightly linked to the formation of reduced iron–sulfide minerals. The possibility of tipping points in the redox state of sediments and oceans, which allow large and nonreversible geochemical shifts to arise from relatively small changes in organic carbon input, has important implications for the interpretation of the geological rock record and the causes and consequences of major evolutionary transitions in the history of Earth’s biosphere.

scholarly journals Conflict and cooperation in eukaryogenesis: implications for the timing of endosymbiosis and the evolution of sex

2015 ◽  
Author(s):  
Arunas L Radzvilavicius ◽  
Neil W Blackstone
Keyword(s):  
Cell Fusion ◽  
Mitochondrial Gene ◽  
Evolutionary Process ◽  
Eukaryotic Cell ◽  
Evolutionary Transition ◽  
Evolutionary Transitions ◽  
Conflict And Cooperation ◽  
Conflict Mediation ◽  
Considerable Debate ◽  
History Of

The complex eukaryotic cell is a result of an ancient endosymbiosis and one of the major evolutionary transitions. The timing of key eukaryotic innovations relative to the acquisition of mitochondria remains subject to considerable debate, yet the evolutionary process itself might constrain the order of these events. Endosymbiosis entailed levels-of-selection conflicts, and mechanisms of conflict mediation had to evolve for eukaryogenesis to proceed. The initial mechanisms of conflict mediation were based on the pathways inherited from prokaryotic symbionts and led to metabolic homeostasis in the eukaryotic cell, while later mechanisms (e.g., mitochondrial gene transfer) contributed to the expansion of the eukaryotic genome. Perhaps the greatest opportunity for conflict arose with the emergence of sex involving whole-cell fusion. While early evolution of cell fusion may have affected symbiont acquisition, sex together with the competitive symbiont behaviour would have destabilised the emerging higher-level unit. Cytoplasmic mixing, on the other hand, would have been beneficial for selfish endosymbionts, capable of using their own metabolism to manipulate the life history of the host. Given the results of our mathematical modelling, we argue that sex represents a rather late proto- eukaryotic innovation, allowing for the growth of the chimeric nucleus and contributing to the successful completion of the evolutionary transition.

scholarly journals The order of trait emergence in the evolution of cyanobacterial multicellularity

2019 ◽  
Author(s):  
Katrin Hammerschmidt ◽  
Giddy Landan ◽  
Fernando Domingues Kümmel Tria ◽  
Jaime Alcorta ◽  
Tal Dagan
Keyword(s):  
Division Of Labor ◽  
Phenotypic Trait ◽  
Evolutionary Transition ◽  
Evolutionary Transitions ◽  
Differentiated Cells ◽  
Labor Theory ◽  
Significant Events ◽  
Reproductive Life ◽  
History Of ◽  
Multicellular Organisms

AbstractThe transition from unicellular to multicellular organisms is one of the most significant events in the history of life. Key to this process is the emergence of Darwinian individuality at the higher level: groups must become single entities capable of reproduction for selection to shape their evolution. Evolutionary transitions in individuality are characterized by cooperation between the lower level entities and by division of labor. Theory suggests that division of labor may drive the transition to multicellularity by eliminating the trade-off between two incompatible processes that cannot be performed simultaneously in one cell. Here we examine the evolution of the most ancient multicellular transition known today, that of cyanobacteria, where we reconstruct the sequence of ecological and phenotypic trait evolution. Our results show that the prime driver of multicellularity in cyanobacteria was the expansion in metabolic capacity offered by nitrogen fixation, which was accompanied by the emergence of the filamentous morphology and succeeded by a reproductive life cycle. This was followed by the progression of multicellularity into higher complexity in the form of differentiated cells and patterned multicellularity.Significance StatementThe emergence of multicellularity is a major evolutionary transition. The oldest transition, that of cyanobacteria, happened more than 3 to 3.5 billion years ago. We find N2 fixation to be the prime driver of multicellularity in cyanobacteria. This innovation faced the challenge of incompatible metabolic processes since the N2 fixing enzyme (nitrogenase) is sensitive to oxygen, which is abundantly found in cyanobacteria cells performing photosynthesis. At the same time, N2-fixation conferred an adaptive benefit to the filamentous morphology as cells could divide their labour into performing either N2-fixation or photosynthesis. This was followed by the culmination of complex multicellularity in the form of differentiated cells and patterned multicellularity.

scholarly journals Redox chemistry of cobalamin and iron-sulfur cofactors in the tetrachloroethene reductase ofDehalobacter restrictus

FEBS Letters ◽  
1997 ◽  
Vol 409 (3) ◽  
pp. 421-425 ◽  
Author(s):  
Wolfram Schumacher ◽  
Christof Holliger ◽  
Alexander J.B Zehnder ◽  
Wilfred R Hagen
Keyword(s):  
Redox Chemistry ◽  
Iron Sulfur

A theoretical study of adsorption on iron sulfides towards nanoparticle modeling

2020 ◽  
Vol 22 (40) ◽  
pp. 23258-23267
Author(s):  
Miroslav Kolos ◽  
Daniel Tunega ◽  
František Karlický
Keyword(s):  
Iron Sulfide ◽  
Theoretical Study ◽  
Sulfide Minerals ◽  
Adsorption Properties ◽  
Zero Valent Iron ◽  
Polar Molecules ◽  
Iron Sulfides ◽  
Iron Sulfide Minerals

The adsorption properties of two iron sulfide minerals (mackinawite and pyrite) and zero-valent iron with respect to two small polar molecules (H2O and H2S) and trichloroethylene (TCE) were modeled.

Mercury removal from water by iron sulfide minerals. An electron spectroscopy for chemical analysis (ESCA) study

1979 ◽  
Vol 13 (9) ◽  
pp. 1142-1144 ◽  
Author(s):  
James R. Brown ◽  
G. Michael Bancroft ◽  
William S. Fyfe ◽  
Ronald A. N. McLean
Keyword(s):  
Chemical Analysis ◽  
Electron Spectroscopy ◽  
Iron Sulfide ◽  
Sulfide Minerals ◽  
Mercury Removal ◽  
Iron Sulfide Minerals

The X-Ray Analysis of Uranium Ores for Iron Sulfide Minerals

1981 ◽  
Vol 25 ◽  
pp. 113-115
Author(s):  
A. J. Durbetaki ◽  
R. H. Carlson ◽  
T. F. Quail
Keyword(s):  
Hydrogen Peroxide ◽  
Iron Sulfide ◽  
Sulfide Minerals ◽  
Ore Deposits ◽  
X Ray Diffraction ◽  
X Ray ◽  
Iron Sulfide Minerals ◽  
Xrd Method

Hydrogen peroxide is used to extract uranium by the in situ leaching of sandstone ore deposits containing uraninite (UO2). Since FeS2 minerals, marcasite and pyrite, also occur in these deposits and they consume hydrogen peroxide in their oxidation, it is important to determine their concentration.A quantitative X-ray diffraction (XRD) method was therefore developed in order to monitor the concentration of marcasite and pyrite in sandstone ores.

scholarly journals Subcritical Instabilities in Neutral Fluids and Plasmas

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 89 ◽  
Author(s):  
Maxime Lesur ◽  
Julien Médina ◽  
Makoto Sasaki ◽  
Akihiro Shimizu
Keyword(s):  
Steady State ◽  
Random Noise ◽  
Finite Amplitude ◽  
Analytical Models ◽  
Space Plasmas ◽  
Fusion Plasmas ◽  
Potential Well ◽  
Small Perturbations ◽  
History Of ◽  
The 1960S

In neutral fluids and plasmas, the analysis of perturbations often starts with an inventory of linearly unstable modes. Then, the nonlinear steady-state is analyzed or predicted based on these linear modes. A crude analogy would be to base the study of a chair on how it responds to infinitesimaly small perturbations. One would conclude that the chair is stable at all frequencies, and cannot fall down. Of course, a chair falls down if subjected to finite-amplitude perturbations. Similarly, waves and wave-like structures in neutral fluids and plasmas can be triggered even though they are linearly stable. These subcritical instabilities are dormant until an interaction, a drive, a forcing, or random noise pushes their amplitude above some threshold. Investigating their onset conditions requires nonlinear calculations. Subcritical instabilities are ubiquitous in neutral fluids and plasmas. In plasmas, subcritical instabilities have been investigated based on analytical models and numerical simulations since the 1960s. More recently, they have been measured in laboratory and space plasmas, albeit not always directly. The topic could benefit from the much longer and richer history of subcritical instability and transition to subcritical turbulence in neutral fluids. In this tutorial introduction, we describe the fundamental aspects of subcritical instabilities in plasmas, based on systems of increasing complexity, from simple examples of a point-mass in a potential well or a box on a table, to turbulence and instabilities in neutral fluids, and finally, to modern applications in magnetized toroidal fusion plasmas.

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