Primitive Life Research Articles

Graphite mineralization in Paleoproterozoic khondalites of the North China Craton: A carbon isotope study

Graphite mineralization in Precambrian supracrustal rocks provide important information on the source characteristics of carbon and has been the focus of studies tracking primitive life in the early Earth as well as a geochemical tracer in fluid-rock interaction processes. Here we present results from a high precision carbon stable isotope study of the different associations of graphites from a graphite deposit in the Paleoproterozoic Khondalite Belt of the North China Craton. Our results show that disseminated graphite occurring as ‘stratabound’ deposits along the compositional planes of the khondalites possess the lowest δ13C values of ca. −25.5‰. Graphite in the massive ores also show identical composition with δ13C values in the narrow range of ca. −25.3 to −25.7‰. Coarse graphite flakes in quartz pods and veins show slightly heavier values with δ13C in the range of −19.1 to −20.9‰; such flakes with δ13C composition of ca. −20.6‰ were also deposited in some domains of the host khondalites. The graphite in melt pockets within felsic leucosomes show the heaviest δ13C values in the range of −15.8 to −16.8‰. Micro-sampling perpendicular to the c-axis of the graphite crystals indicates a remarkable homogeneity of carbon isotopic composition within the individual graphite types. The highly negative δ13C values of the dominant graphite type in this deposit, as well as similar values reported for those from other deposits in the region, compare well with the isotopic signature of biogenic carbon occurring in other Precambrian terranes and suggest that microbial life was flourishing in the Paleoproterozoic oceans that closed during the final assembly of the North China Craton. The 13C enriched graphite in veins and melt pockets might have been deposited from mixed fluids derived through degassing of organic material during high grade metamorphism and externally-derived CO2-rich fluids

Chemical Synthesis in Small Spaces

Can miniscule reaction chambers such as atmospheric aerosol droplets [1], prebiotic aerosols [2], or microscale compartments discovered at hydrothermal vents [3] enhance chemical synthesis? A variety of natural processes rely on chemical synthesis within mesoscale confinements, including those that may have resulted in primitive life forms arising from a collection of nonliving molecules [2–4]. It is known, however, that entropic contributions thermodynamically disfavor synthesis reactions; for example, formation of one product molecule from two reactant molecules results in a high loss of mobility and thereby a decrease in entropy [5]. A report in Physical Review Letters by Ali Fallah-Araghi at the University of Strasbourg, France, and colleagues [6] describes a universal mechanism that could help overcome the thermodynamic unfavorability of these reactions. Specifically, they argue that these synthesis reactions are more favorable if they take place in a microcompartment than if they occur without confinement.

Management of Extremely Long Sinus Pauses in a Child with Primitive Neuroectodermal Tumor and Apparent Life Threatening Events: A Case Report

A male child, three years old, with primitive neuroectodermal tumor (PNET) was admitted to our department because of episodes of apnea with syncope. Twenty four hr ambulatory electrocardiographic monitoring revealed extremely long sinus pauses, the longest being thirty four seconds, followed by sinus tachycardia. Permanent pacing reduced the frequency, duration and severity of episodes.

Seeding Life on the Moons of the Outer Planets via Lithopanspermia

Material from the surface of a planet can be ejected into space by a large impact and could carry primitive life-forms with it. We performed n-body simulations of such ejecta to determine where in the Solar System rock from Earth and Mars may end up. We found that, in addition to frequent transfer of material among the terrestrial planets, transfer of material from Earth and Mars to the moons of Jupiter and Saturn is also possible, but rare. We expect that such transfers were most likely to occur during the Late Heavy Bombardment or during the ensuing 1-2 billion years. At this time, the icy moons were warmer and likely had little or no ice shell to prevent meteorites from reaching their liquid interiors. We also note significant rates of re-impact in the first million years after ejection. This could re-seed life on a planet after partial or complete sterilization by a large impact, which would aid the survival of early life during the Late Heavy Bombardment.

Hospitable Archean Climates Simulated by a General Circulation Model

Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model.

Adenosine Monophosphate Forms Ordered Arrays in Multilamellar Lipid Matrices: Insights into Assembly of Nucleic Acid for Primitive Life

A fundamental question of biology is how nucleic acids first assembled and then were incorporated into the earliest forms of cellular life 4 billion years ago. The polymerization of nucleotides is a condensation reaction in which phosphodiester bonds are formed. This reaction cannot occur in aqueous solutions, but guided polymerization in an anhydrous lipid environment could promote a non-enzymatic condensation reaction in which oligomers of single stranded nucleic acids are synthesized. We used X-ray scattering to investigate 5′-adenosine monophosphate (AMP) molecules captured in a multilamellar phospholipid matrix composed of dimyristoylphosphatidylcholine. Bragg peaks corresponding to the lateral organization of the confined AMP molecules were observed. Instead of forming a random array, the AMP molecules are highly entangled, with the phosphate and ribose groups in close proximity. This structure may facilitate polymerization of the nucleotides into RNA-like polymers.

Health Benefits of Blue-Green Algae: Prevention of Cardiovascular Disease and Nonalcoholic Fatty Liver Disease

Blue-green algae (BGA) are among the most primitive life forms on earth and have been consumed as food or medicine by humans for centuries. BGA contain various bioactive components, such as phycocyanin, carotenoids, γ-linolenic acid, fibers, and plant sterols, which can promote optimal health in humans. Studies have demonstrated that several BGA species or their active components have plasma total cholesterol and triglyceride-lowering properties due to their modulation of intestinal cholesterol absorption and hepatic lipogenic gene expression. BGA can also reduce inflammation by inhibiting the nuclear factor κ B activity, consequently reducing the production of proinflammatory cytokines. Furthermore, BGA inhibit lipid peroxidation and have free radical scavenging activity, which can be beneficial for the protection against oxidative stress. The aforementioned effects of BGA can contribute to the prevention of metabolic and inflammatory diseases. This review provides an overview of the current knowledge of the health-promoting functions of BGA against cardiovascular disease and nonalcoholic fatty liver disease, which are major health threats in the developed countries.

The Pilagá of the Argentine Chaco through an exoticizing and ethnographic lens: The Swedish documentary film Following Indian trails by the Pilcomayo River

In this article, we explore how traveling relates to image production and how transcultural filmic representations both uphold and are sustained by a “coloniality of seeing.” We pay special attention to the historical conditions of film making in an expedition context and the expectations associated with early film in Sweden. We discuss this through the study of the documentary film Following Indian Trails by the Pilcomayo River, which was recorded during a Swedish expedition to the Argentine Chaco in 1920 and later released in Stockholm in 1950 during a private screening organized by the Swedish Chaco Travellers Association. We argue that the film presents an account inspired by classic ethnography which rescues and puts into circulation images of indigenous people from the “impenetrable” and “savage” Chaco. The ethnographic emphasis in the narrative seems to have shifted with time as it was probably only partly present during the shooting of the footage. In the narrative mode of “monstration,” when bodies meet machines “in the field,” native performances are presented as an “unstaged” and realist spectacle. Later in the 1950 macro-“narration,” encompassing the final cutting and editing of the original footage, fragments of spectacle are systematized into an ethnographic description of primitive life.

α‐Complementation in an Artificial Genome Replication System in Liposomes

Genome size is considered one of the limiting factors for the replication of primitive life forms. However, the relationship between genome size and replication efficiency has not been tested experimentally. In this study, we examined the effect of genome size on genome replication by using an artificial cell model: a self-replicating RNA genome encapsulated in a liposome. For the reduced genome size we used α-complementation of the lacZ gene. We first characterized α-complementation in the purified translation system and then applied α-complementation to the genome replication system. The reduction in the genome size together with the addition of ω-fragment increased the replication efficiency approximately eightfold. This result provides experimental evidence that genome size can be a limiting factor for primitive self-replication systems; it also implies that this artificial cell model could be a useful experimental model to identify possible mechanisms of genome enlargement.

The naked planet Earth: Most essential pre-requisite for the origin and evolution of life

Our blue planet Earth has long been regarded to carry full of nutrients for hosting life since the birth of the planet. Here we speculate the processes that led to the birth of early life on Earth and its aftermath, finally leading to the evolution of metazoans. We evaluate: (1) the source of nutrients, (2) the chemistry of primordial ocean, (3) the initial mass of ocean, and (4) the size of planet. Among the life-building nutrients, phosphorus and potassium play a key role. Only three types of rocks can serve as an adequate source of nutrients: (a) continent-forming TTG (granite), enabling the evolution of primitive life to metazoans; (b) primordial continents carrying anorthosite with KREEP (Potassium, Rare Earth Elements, and Phosphorus) basalts, which is a key to bear life; (c) carbonatite magma, enriched in radiogenic elements such as U and Th, which can cause mutation to speed up evolution and promote the birth of new species in continental rift settings. The second important factor is ocean chemistry. The primordial ocean was extremely acidic (pH = 1–2) and enriched in halogens (Cl, F and others), S, N and metallic elements (Cd, Cu, Zn, and others), inhibiting the birth of life. Plate tectonics cleaned up these elements which interfered with RNA. Blue ocean finally appeared in the Phanerozoic with pH = 7 through extensive interaction with surface continental crust by weathering, erosion and transportation into ocean. The initial ocean mass was also important. The birth of life and aftermath of evolution was possible in the habitable zone with 3–5 km deep ocean which was able to supply sufficient nutrients. Without a huge landmass, nutrients cannot be supplied into the ocean only by ridge-hydrothermal circulation in the Hadean. Finally, the size of the planet plays a crucial role. Cooling of massive planets is less efficient than smaller ones, so that return-flow of seawater into mantle does not occur until central stars finish their main sequence. Due to the suitable size of Earth, the dawn of Phanerozoic witnessed the initiation of return-flow of seawater into the mantle, leading to the emergence of huge landmass above sea-level, and the distribution of nutrients on a global scale. Oxygen pump also played a critical role to keep high-PO2 in atmosphere since then, leading to the emergence of ozone layer and enabling animals and plants to invade the land.To satisfy the tight conditions to make the Earth habitable, the formation mechanism of primordial Earth is an important factor. At first, a ‘dry Earth’ must be made through giant impact, followed by magma ocean to float nutrient-enriched primordial continents (anorthosite + KREEP). Late bombardment from asteroid belt supplied water to make 3–5 km thick ocean, and not from icy meteorites from Kuiper belt beyond cool Jupiter. It was essential to meet the above conditions that enabled the Earth as a habitable planet with evolved life forms. The tight constraints that we evaluate for birth and evolution of life on Earth would provide important guidelines for planetary scientists hunting for life in the exo-solar planets.

Silica Biomorphs: Complex Biomimetic Hybrid Materials from “Sand and Chalk”

AbstractBiomineralization can afford crystal frameworks of great diversity and utmost complexity, frequently featuring hierarchical structures and morphologies beyond any crystallographic restrictions. The formation of such architectures is usually directed by organic molecules or matrices, which modify crystallization in a deliberate manner. Their influence often leads to sinuous forms, which, by intuition, suggest the presence of life and distinguish these minerals from their inanimate, mostly euhedral counterparts. However, such a strict distinction does not hold. In fact, smooth curvature and higher‐order structuring can occur also in purely inorganic environments: simply by precipitating alkaline earth carbonates in silica‐containing media, aggregates of highly oriented carbonate nanocrystals can be obtained that display striking noncrystallographic morphologies such as regular helicoids. Thereby, individual crystallites as well as the entire assembly are sheathed by amorphous silica, thus giving a composite material with various levels of hierarchy. These exceptional forms, called “silica biomorphs”, self‐assemble through a bottom‐up process, which relies on local variations in the conditions and is driven by a pH‐based coupling of the carbonate and silicate. Here, we review recent progress in the field of silica biomorphs with particular focus on their mechanism of formation, provide insight into structural details at different length scales, and discuss implications of these biomimetic crystal aggregates for both primitive life detection and materials science.

Viruses in Biology

AbstractDuring the first half of the twentieth century, many scientists considered viruses the smallest living entities and primitive life forms somehow placed between the inert world and highly evolved cells. The development of molecular biology in the second half of the century showed that viruses are strict molecular parasites of cells, putting an end to previous virocentric debates that gave viruses a primeval role in the origin of life. Recent advances in comparative genomics and metagenomics have uncovered a vast viral diversity and have shown that viruses are active regulators of cell populations and that they can influence cell evolution by acting as vectors for gene transfer among cells. They have also fostered a revival of old virocentric ideas. These ideas are heterogeneous, extending from proposals that consider viruses functionally as living beings and/or as descendants of viral lineages that preceded cell evolution to other claims that consider viruses and/or some viral families a fourth domain of life. In this article, we revisit these virocentric ideas and analyze the place of viruses in biology in light of the long-standing dichotomic debate between metabolist and geneticist views which hold, respectively, that self-maintenance (metabolism) or self-replication and evolution are the primeval features of life. We argue that whereas the epistemological discussion about whether viruses are alive or not and whether some virus-like replicators precede the first cells is a matter of debate that can be understood within the metabolism-versus-genes dialectic; the claim that viruses form a fourth domain in the tree of life can be solidly refuted by proper molecular phylogenetic analyses and needs to be removed from this debate.

The touching story of purinergic signaling in epithelial and endothelial cells

Endothelial and epithelial cells have something in common—they are both the barrier and bridge between different environments. Forming a one-cell layer lining of blood vessels, airways, and urinary tract, they are in constant contact with a wide variety of cells, putting high demands on the communication skills of these cells. The purinergic signaling system offers a dynamic and versatile way for local and rapid intercellular communication and involves three processes: nucleotide release, enzymatic degradation, and activation of purinergic receptors. With an impressive number of molecular members of the system (15 P2 receptor subtypes and in total 16 nucleotide-degrading enzymes), cells have managed to put purines and pyrimidines as well as their derivatives to use in an array of different areas, including regulation of flow, secretion, and vascular tone. Indeed, the purinergic signaling system is an ancient way of intercellular communication that most likely could be found in the first most primitive life form [1]. The scope of this review is to give an overview of exciting features of purinergic signaling and examples of gaps to fill in understanding its role in the cells lining the body—the endothelium and the epithelium.

Decadence in the Wilderness. Will to Transgression or the Strange Bird of Finnish Decadence

The decadence that the Decadents identified in their own civilization was recognized through the model of Roman Empire, although they thought that the Romans were, even in their decadence, much more vigorous than the modern "cerebral" decadents. The figures of the late Empire, which fused the over-ripeness of culture with barbarism, were great even in their decline; the ancient uninhibited transgressions and vices fascinated the decadents although even the imagined debaucheries exhausted the modern decadents. Des Esseintes is, of course, a paradigmatic figure, connecting extreme weakness and fragility of the nervous system with wild sadistic dreams. He is capable of producing vigorous mental images, imagining sublimely horrible figures and emblems of disease, which fell on a fertile ground in later decadent writings.At the same time, the idea of the savage and the primitive which had underwent a radical change, when the romantic idea of the noble savage was replaced by the primitive as the lowest order of humanity, became fashionable even among many Decadents. This debauched barbarian or savage (whose representatives or relics the survived "primitive cultures" were) marked the beginnings of human culture and was the suppressed foundation of all developed cultures. The danger of the return of this primitive side of man could threaten even the most civilized individuals or nations if the ties and restraints of culture were loosened (Joseph Conrad's Heart of Darkness represents this perfectly). For the decadents, who did not see their own civilization in the terms of progress any more, and embraced ideas of entropy, dissolution and return to a state of new barbarism, the idea of the decline of their culture, thus, could become connected with the idea of the primitive "in us", the primitive lurking in the psyche of every individual and the primitive that was built in the culture itself. As the primitive became, increasingly, identified not only with "primitive peoples" or "primitive races" mostly inhabiting in the colonies or far-out regions, but with groups within the civilized society, like workers, paupers, lower classes, Jews or even women, it was easy to find seeds and forces of the foreseen and, at the same time, feared development. When these ideas were connected with Nietzscheanism, like in the early novels by the Finnish author Joel Lehtonen, they produced a provocative form of Dionysian Decadence; a manic form of decadence combining primitive energies with provocative questioning of traditional cultural values. It was Nietzsche himself who suggested the idea that the "tropical man" or the primitive seen as the evil to be eradicated by the moralists should be recognized as a potentially positive force (Beyond Good and Evil, 197). Lehtonen's decadent figures (especially in his novel Mataleena 1905) find their roots in the primitive life of the Finnish "wilderness" and connect this primitiveness to a provocative decadence, which is à rebours, against all recognized cultural values but has power only as a form of deconstruction and destruction.

On dating stages in prebiotic chemical evolution

The notion that RNA must have had a unique and decisive role in the development of life needs hardly be questioned. However, the chemical complexity and other properties of RNA, such as high solubility in water and vulnerability to degradation, make it improbable that RNA could have had an early presence in the development of life on Earth or on any comparable telluric planet. Rather, the task of origin of life research must surely be to identify those chemical processes which could have taken place on Earth that could accumulate the complexity and rich molecular information content needed to sustain primitive life, and ultimately give rise to RNA. A collection of likely chemical precursors to modern biomolecules is listed here together with calculations of their molecular complexity. These complexity scores are then used to propose an ordering, on a timescale, of when they might have appeared on Earth. These pre-RNA living systems would have flourished during the first ~0.3 Gyrs after the start of the Archaean era (~4.2 Gyr ago). If there ever was an "RNA-world" it could have started after that initial period (~3.9 Gyrs ago), later to be complemented with the appearance of duplex DNA at about ~3.6 Gyrs ago, some time before the earliest known stromatolites (~3.4 Gyr).

The genes and enzymes of phosphonate metabolism by bacteria, and their distribution in the marine environment

Phosphonates are compounds that contain the chemically stable carbon–phosphorus (C–P) bond. They are widely distributed amongst more primitive life forms including many marine invertebrates and constitute a significant component of the dissolved organic phosphorus reservoir in the oceans. Virtually all biogenic C–P compounds are synthesized by a pathway in which the key step is the intramolecular rearrangement of phosphoenolpyruvate to phosphonopyruvate. However C–P bond cleavage by degradative microorganisms is catalyzed by a number of enzymes – C–P lyases, C–P hydrolases, and others of as-yet-uncharacterized mechanism. Expression of some of the pathways of phosphonate catabolism is controlled by ambient levels of inorganic P (Pi) but for others it is Pi-independent. In this report we review the enzymology of C–P bond metabolism in bacteria, and also present the results of an in silico investigation of the distribution of the genes that encode the pathways responsible, in both bacterial genomes and in marine metagenomic libraries, and their likely modes of regulation. Interrogation of currently available whole-genome bacterial sequences indicates that some 10% contain genes encoding putative pathways of phosphonate biosynthesis while ∼40% encode one or more pathways of phosphonate catabolism. Analysis of metagenomic data from the global ocean survey suggests that some 10 and 30%, respectively, of bacterial genomes across the sites sampled encode these pathways. Catabolic routes involving phosphonoacetate hydrolase, C–P lyase(s), and an uncharacterized 2-aminoethylphosphonate degradative sequence were predominant, and it is likely that both substrate-inducible and Pi-repressible mechanisms are involved in their regulation. The data we present indicate the likely importance of phosphonate-P in global biogeochemical P cycling, and by extension its role in marine productivity and in carbon and nitrogen dynamics in the oceans.

Self-Replication Reactions Dependent on Tertiary Interaction Motifs in an RNA Ligase Ribozyme

RNA can function both as an informational molecule and as a catalyst in living organisms. This duality is the premise of the RNA world hypothesis. However, one flaw in the hypothesis that RNA was the most essential molecule in primitive life is that no RNA self-replicating system has been found in nature. To verify whether RNA has the potential for self-replication, we constructed a new RNA self-assembling ribozyme that could have conducted an evolvable RNA self-replication reaction. The artificially designed, in vitro selected ligase ribozyme was employed as a prototype for a self-assembling ribozyme. The ribozyme is composed of two RNA fragments (form R1·Z1) that recognize another R1·Z1 molecule as their substrate and perform the high turnover ligation reaction via two RNA tertiary interaction motifs. Furthermore, the substrate recognition of R1·Z1 is tolerant of mutations, generating diversity in the corresponding RNA self-replicating network. Thus, we propose that our system implies the significance of RNA tertiary motifs in the early RNA molecular evolution of the RNA world.

Humanity and Sustainability

So far our open access publishing company MDPI (Multidisciplinary Digital Publishing Institute) has published mainly science, medicine and technology journals. To become a multidisciplinary publisher, we launched the journal Sustainability [1]. More recently, we started to run several social science journals, including Societies [2], Religions [3], Administrative Sciences [4] and Behavioral Sciences [5]. Today we published the first paper [6] of the inaugural issue of Humanities (ISSN 2076-0787). This will be an international open access journal, publishing scholarly papers of high quality across all humanities disciplines. As a publisher, I would like to publish journals surrounding the topics of sustainability and I believe the humanities as a discipline of academic studies are very important. As a scientist, I believed science and technology will only benefit human beings. I was raised in a small village, living a very primitive life in a peasant family: no electricity, no machines, of course no TV and no refrigerator. Now, the life of my children is completely different. Even my own life has completely changed. I have witnessed very rapid changes: more and more machines are used to consume mineral resources and energy and to pollute the environment, in order to produce more and more powerful machines (we are also launching a journal titled Machines, in which the relationship between Man and machine should be an interesting topic.). Machines are more and more like human individuals consuming resources themselves (we are launching a journal titled Resources). [...]

Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod

Virtually all species have developed cellular oscillations and mechanisms that synchronize these cellular oscillations to environmental cycles. Such environmental cycles in biotic (e.g. food availability and predation risk) or abiotic (e.g. temperature and light) factors may occur on a daily, annual or tidal time scale. Internal timing mechanisms may facilitate behavioural or physiological adaptation to such changes in environmental conditions. These timing mechanisms commonly involve an internal molecular oscillator (a 'clock') that is synchronized ('entrained') to the environmental cycle by receptor mechanisms responding to relevant environmental signals ('Zeitgeber', i.e. German for time-giver). To understand the evolution of such timing mechanisms, we have to understand the mechanisms leading to selective advantage. Although major advances have been made in our understanding of the physiological and molecular mechanisms driving internal cycles (proximate questions), studies identifying mechanisms of natural selection on clock systems (ultimate questions) are rather limited. Here, we discuss the selective advantage of a circadian system and how its adaptation to day length variation may have a functional role in optimizing seasonal timing. We discuss various cases where selective advantages of circadian timing mechanisms have been shown and cases where temporarily loss of circadian timing may cause selective advantage. We suggest an explanation for why a circadian timing system has emerged in primitive life forms like cyanobacteria and we evaluate a possible molecular mechanism that enabled these bacteria to adapt to seasonal variation in day length. We further discuss how the role of the circadian system in photoperiodic time measurement may explain differential selection pressures on circadian period when species are exposed to changing climatic conditions (e.g. global warming) or when they expand their geographical range to different latitudes or altitudes.

DRAKE EQUATION FOR THE MULTIVERSE: FROM THE STRING LANDSCAPE TO COMPLEX LIFE

It is argued that the selection criteria usually referred to as "anthropic conditions" for the existence of intelligent (typical) observers widely adopted in cosmology amount only to preconditions for primitive life. The existence of life does not imply in the existence of intelligent life. On the contrary, the transition from single-celled to complex, multicellular organisms is far from trivial, requiring stringent additional conditions on planetary platforms. An attempt is made to disentangle the necessary steps leading from a selection of universes out of a hypothetical multiverse to the existence of life and of complex life. It is suggested that what is currently called the "anthropic principle" should instead be named the "prebiotic principle."