Emergence of Life and Exobiology PDF

Emergence of life and exobiology Prof. Patrizia Contursi Email: [email protected] Website: https://www.docenti.unina.it/patrizia.contursi Room: 1D-01 Edificio 7 Tel: 081-679166 Link to TEAM CLASS: https://teams.microsoft.com/l/team/19%3aAxKKLB9N- SKV1Btc6jIBfXv5HnPZopFds5_4Fo52ZLA1%40thread.tacv2/conversations?groupId=979e0eed-bc41-4a29-85f8- 1057e8a9b331&tenantId=2fcfe26a-bb62-46b0-b1e3-28f9da0c45fd Team code: 0mmbmjs Exam: only oral Objectives: This course aims to provide knowledge regarding the synergistic role of biotic and abiotic factors that influenced the origin of life on Earth. It also aims to describe the state of the art of the experimental approaches concerning the search for extraterrestrial life forms Prerequisites: Knowledge of Microbiology, Biochemistry, Molecular Biology, Chemistry Teaching material: The Origins and Search for Life (English Edition) di Edward Trifonov, Nick Lane, Stephen Freeland, Michael Russell Biosignatures for Astrobiology, Editors: Cavalazzi, Barbara, Westall, Frances (Eds.) Scientific papers, Reviews (Note of the course) The pdf of the slides will be made available, which can be downloaded from the teacher website Program: Definition of life Origin of life: introductory concepts and comparison of hypotheses on the origin and evolution of life (first metabolism, first genes, first vesicles). Analysis of evolutionary relationships by molecular analysis (homologues, paralogues, orthologues and horizontal gene transfer mechanisms). Extremophile viruses and the origin of life: isolation and identification of viruses and plasmids in extreme environments (metaviromics); virus-host interaction (CRISPR, manipulative genetics); Role of genetic elements in the horizontal transfer of genes, analysis of viral genomes; Identification of "core genes" within the different families of viral genomes. Exobiology: Concept of biosignatures and planetary habitability; classification of biosignatures: gaseous, superficial (photosynthesis and pigments) and with temporal oscillation. Introductory concepts to sample return (technical, temporal and procedural limitations); identification of sampling sites and methods; analysis of biological systems in extraterrestrial conditions. Introductory concepts on synthetic life. Scheme of the course Lessons External seminars (onlone and in presence): Prof. Patrick Forterre, Pasteur Institute (Last universal common ancestor, viruses and origin of life) Prof. Xu Peng, University of Copenaghen (Prokaryotic viruses and CRISPR and anti CRISPR) Prof. Laura Martinez, University of Copenaghen (Metaviromics anaòysis) Dr. Giovanni Gallo, Ludwig-Maximilians-Universität München · (CRISPR as genome editing tools) Dr. Martina Aulitto, Università Federico II, Dpt Biologia (Top down approach to study life origin, Phylogenetic trees etc) Dr. Monica Piochi, Istituto Nazionale di Geofisica e Vulcanologia (Geological features of possible locations related to the origin of life) Prof. Nicola Napletano, Università di Napoli, Dpt, Fisica Dr. Afonso Morgada Mota, Centro de Astrofísica da Universidade do Porto, Portugal (exobiology) One day trip sampling Student Seminars on topics selected by the students RESEARCH LINES Setting up of genetic Biochemistry and Molecular systems for Archaea Biology of archaeal viruses Genomics and metagenomics Exploitation of thermophiles in of enviromental samples biotechnological research DEFINITION OF LIFE Controversy about the scientific meaning of life Life and living being Exobiology and the search of new life forms: The Viking mission (1976) LIFE DEFINING ‘LIFE’ The scientiﬁc literature is ﬁlled with suggestions...There is no broadly accepted deﬁnition of ‘life.’ DEFINING ‘LIFE’ Alive versus being part of a living system "What is life?" asks about the *scientific* or *biological* characteristics that define what makes something "alive." It's about the essential processes that living organisms (whether plants, animals, fungi, or bacteria) share. This is universal to all forms of life. *For example*: All living things grow, reproduce, respond to stimuli, and maintain internal balance. These are the core features that qualify something as being alive. "What does it mean to be alive?" can be understood as a more *philosophical* or *experiential* question, which delves into what it feels or means to live. It’s less about biology and more about the *experience* of life—especially consciousness, emotions, self-awareness, and purpose. *For example*: Animals, humans, and potentially some other organisms experience being alive through sensation, emotions, or awareness, but plants, while alive, don’t have the same conscious experience of being alive. What is life? So, while **both questions** are related to the concept of life, the first focuses on *what makes something biologically alive*, and the second explores *what it means, experientially or philosophically, to be alive*. Both vs apply to all life in the sense that they are fundamental questions about existence, but the second question can lean more into the subjective experience, which is more applicable to sentient beings (like animals and humans) than to plants or microorganisms. What does it mean to be alive??? The Controversy Surrounding Life The question of what constitutes "life" is often distinguished between the concept of being alive and being part of a living system. While we can observe living organisms and their behaviors, the underlying principles that define life are less clear. For instance, life on Earth is primarily built around compounds containing essential elements, such as carbon, nitrogen, hydrogen, and oxygen. Collectively, these elements, along with phosphorus and calcium, constitute about 97-99% of the dry weight of living organisms. The composition of living matter is markedly different from that of inanimate objects, underscoring the complexity of defining life. MOLECULAR LEVEL Life on Earth is built around compounds that contain elements such as carbon, nitrogen, hydrogen and oxygen Certain elements universally present in all organisms others appear only in specific types The most abundant elements found in all living organisms include carbon, hydrogen, nitrogen, and oxygen. Additional elements such as calcium, magnesium, phosphorus, potassium, sodium, and sulfur, while less abundant, are also vital for various biological functions. Trace metals, like cobalt, copper, iron, manganese, and zinc, are essential in small quantities, playing critical roles in enzymatic reactions and cellular processes. These trace elements contribute to the unique chemistry of life, which is organized around carbon. chnops are low atomic number -> essential because they make stronger bonds than elements with higher atomic number Element Present in all Present in some organisms organisms C, H, O, N, P, Ca Carbon X The most e S constitute Hydrogen X abundant in all Nitrogen X organisms about 97-99% Oxygen X of the dry Clacium X weight of Chloride X Less abundant but Magnesium X present in all livings Phosphorus X organisms Potassium X Sodium X Sulfur X The Cobalt X Metals present in composition of Copper X small quantities Iron X but essential for living matter is Manganese X life remarkably Zinc X different from Aluminum X Arsenic X that of the Boron X Present or inanimate Bromine X required in traces Chrome X by some organisms world Fluorine X Gallium X Iodine X Molybdenum X Selenium X Silicon X Vanadium X The chemistry of living organisms is organized around carbon hydrocarbons (C-H) are not very rective in cels so these H attached to the C are replaced by other elements so this C molecule gets more reactive The chemistry of living organisms relies on carbon's ability to form covalent bonds, resulting in complex biomolecules. Carbon atoms can create linear chains, branched chains, and cyclic structures, which serve as the backbone for essential biological macromolecules. Proteins, polysaccharides, and nucleic acids are made up of a variety of monomeric subunits, demonstrating a modular organization fundamental to life. Covalently linked carbon atoms in biomolecules can form linear chains, branched chains, and cyclic structures The common chemical basis for life strongly supports the idea that all life on Earth is related and descended from a single universal ancestor (LUCA) Proteins, polysaccharides and nucleic acids are made up of a large number of monomeric subunits (modular organization) CHARBOHYDRATES (CH20)n Energy reserve: Stored as glycogen or starch for later use. Fuels: Provide immediate energy through glucose metabolism. Energy reserve Metabolic intermediates: Central in pathways like glycolysis and the citric acid cycle. DNA/RNA scaffolding: Form the sugar backbone of nucleotides. Structural elements: Polysaccharides strengthen bacterial cell walls (peptidoglycan), plant cells (cellulose), and connective tissues. Fuels Glycoproteins & glycolipids: Key for membrane structure and signaling. Cellular interactions: Facilitate cell recognition and communication. Metabolic Intermediates Scaffolding of DNA and RNA Polysaccharides are structural and protective elements in the cell wall of bacteria, plants and connective tissue Glycoproteins and glycolipids Mediators of cellular interactions NUCLEIC ACIDS PROTEINS Conservation and Catalytic activity transmission of Structure genetic information, Signal reception structural role and Transport catalysis etc Types of Biomolecules Carbohydrates: These are vital for energy storage, serving as fuels and LIPIDS metabolic intermediates. They also contribute to the structural integrity of cells, such as in the cell walls of bacteria and plants. Nucleic Acids: Nucleic acids, such as DNA and RNA, are crucial for the conservation and transmission of genetic information, as well as performing structural and catalytic roles. Proteins: Proteins are essential for various functions, including catalytic activity, structural support, signal reception, and transport. Lipids: These molecules play key roles in energy storage, cell membrane structure, and signaling processes. hydrogen donor molecules and acceptor molecules bonds are hydrogen bonds!!!! water is polar CELLULAR LEVEL ORGANISATION Cells are the smallest unit of an organism that can be considered “alive” d. Energy flow occurs within cells The beginnings of cell theory: Schleiden, Schwann, e. Heredity information (DNA) is and Virchow passed on from cell to cell f. All cells have the same basic chemical composition also archaea, all prokaryotes are unicellular what does it mean to be alive: search for homeostasis, reproduce, evolve + grow + develop, respond to environment, obtain and use energy HOMEOSTASIS Living Organisms Maintain a Stable Chemio-physical Internal Environment Organisms need to keep conditions inside their bodies as much constant as possible: Osmoregulation – The maintenance by an organism of an internal balance between water and dissolved minerals regardless of environmental conditions. Thermoregulation – Maintaining an optimal internal temperature. Glucoregulation – The regulation of blood sugar. Etc Response to Stimuli (Signal intracellular or extracellular to which an organism responds) Living Things Respond to Their Environment Living things respond to stimuli to improve their chances for survival Receptors detect stimuli. METABOLISM All life forms on Earth share the same fundamental biochemical processes Living Things Obtain and Use Energy Energy is obtained and used to grow, develop and reproduce Metabolism: The total sum of all chemical reactions in the cell In asexual reproduction, whether the "mother cell" continues to exist or is entirely split into two daughter cells depends on the specific mechanism: 1. **Binary Fission** (e.g., in bacteria): - The mother cell splits into two identical daughter cells, and the original mother cell REPRODUCTION no longer exists as a separate entity. - Both daughter cells are genetically identical and function as new individuals. 2. **Budding** (e.g., in yeast): - The mother cell remains intact and produces a smaller daughter cell (a bud) that eventually detaches. - In this case, the mother cell survives and can continue producing more buds. 3. **Fragmentation or Spore Formation** (e.g., in some fungi): - The original structure may break into parts (fragments) or produce spores, but the original cell's fate depends on the specific organism and process. In summary: In **binary fission**, the mother cell effectively "splits" and ceases to exist, while in **budding**, the mother cell survives. Sexual Reproduction Asexual Reproduction Sexual Reproduction: The mixing of genetic material from 2 members of the same species (the combination of the reproductive cells from two individuals forms a third unique offspring) Asexual Reproduction: Offspring are genetically identical to the parent. No mixing of genetic material. (Binary fission such as in Amoeba, bacteria, production of spores as in fungi, and the formation of tubers in potatoes. Organisms that reproduce asexually usually are found in stable environments to which they are very well suited) EVOLUTION Taken as a Group, Living Things Evolve Basic traits individual organisms inherit from their parents usually do not change. Over many generations, groups of organisms typically evolve or change over time. GROWTH and DEVELOPMENT Living organisms have genetic materials encoding for their development and growth that is sustained by several metabolic processes taking place at the cost of energy in the body Central dogma of Biology All life on Earth share the same fundamental chemical processes Genomic information is stored as dsDNA, transcribed into RNA, and translated into protein The standard genetic code (SGC) is virtually universal among extant life forms VIRUSES DEFY THE CENTRAL DOGMA: ARE VIRUSES ALIVE? central dogma: DNA -> RNA -> protein: replication->transcription->translation the fuction of protein is stored in DNA (sequence) and transcribed and transltion to get function to work The 3D structure of a protein is determined by the amino acid sequence The function of a protein depends on its structure Viruses can store their genomic information in different forms and can replicate in ways against the Central Dogma The many modes of replication and the diversity of replication machineries encoded by viruses offer tantalizing clues to possible alternative modes of replication on Earth before the emergence of DNA-based genomes. BONUS: Virus Is It Alive? DEFINING ‘LIFE Definition is a statement that explains the meaning of a word or a phrase Suggested deﬁnitions face problems, often in the form of robust counter-examples. Deﬁning ‘life’ currently poses a dilemma analogous to that faced by those hoping to deﬁne ‘water’ before the existence of molecular theory listing features is not the same as a definition (see below exampel of water) Let’s try to define the water….. Water is H2O: the development of molecular theory Sensible properties of water: made an unambiguous understanding of ‘water’ wet, odorless, tasteless, and thirst possible quenching also other things have same features and are not water There is need of a theory of biology that allows to attain a deep understanding of the nature of life and formulate a precise theoretical identity for life comparable to the statement ‘water is H20. The ‘chemical Darwinian’ deﬁnition of life has been proposed by NASA: ‘Life is a self-sustained chemical system capable of undergoing Darwinian evolution.’ What life is, but also of what we recognize as its origin. LIFE is a Chemical system: Most of the living systems are made of diverse collection of molecules that interact physically and functionally to carry out all the cellular activities connected with life LIFE is self-sustained: A living system is able to gather molecules and energy sources from the environment LIFE undergoes to Darwinian evolution: Living systems adapt to their environment through accumulation of mutations during reproduction (DNA replication is a not perfect biological process) Charatheristics of life have some exceptions…. Can we consider mule (Zebra and donkey hybrid) as non living since they cannot reproduce? How about the primordial protocell that were able to reproduce without replication (Darwinian evolution was not yet established)? Should we consider a virus as a living entity? Darwinian evolution is also possible for molecules. Long RNA strands that translate into proteins. The faster the translation is done by evolving the RNA strand in shorter RNA strands with the pieces that translate faster. 1. RNA molecules evolve over time, with the "fittest" variants being selected for their efficiency in performing a specific function. 2. long RNA strands are referring to sequences of RNA that code for proteins. 3. Translation refers to the process of synthesizing proteins based on the instructions in RNA. Faster translation would mean that the RNA is able to produce the corresponding protein more efficiently, which could be advantageous in certain environments or conditions. 4. Over time, RNA molecules might evolve into shorter versions of themselves. These shorter strands may be more efficient in terms of translation speed or protein production. This process could involve trimming down the RNA to eliminate non-functional parts, leading to a more streamlined and effective molecular structure. 5. Just like in Darwinian evolution, RNA strands that translate into proteins faster would be "selected" because they are more effective at performing their job. Shorter RNA strands with segments that produce proteins more quickly may be favored, and those that don't translate efficiently may be discarded or evolve into more optimized versions. The problem of defining life is related to the interest towards seeking for new extraterrestrial life forms or synthesis of new life forms How about extreterrestrial life? Should they have the same features of terrestrian creatures? How to know if you detect life? For example, gasses from metabolisms or other activity may be coming from a life form. You can change abiotic conditions, for example the temperature to above a maximal possible temperature where life survives, and then look whether or not you still have the signal. Then you know if the gas is bioticly or abiotically produced. The Viking Mission to Mars Cape Canaveral, Florida, 1975: Viking 1: left on August 20, 1975, landed July 20, 1976, and continued sending data until November 11, 1982. Viking 2 launched September 9, 1975 and operated on Mars until 1980 The objective of these missions was to obtain high resolution images of the Martian surface, characterize the structure and composition of the atmosphere and surface, and search for evidence of life. Immagini dai siti https://mars.nasa.gov/marsexploration/missions/viking-1-2/ https://tsi.com/blog/tsi-blogs/research-academia-blog/august-2019/tsi-and-the-viking-mission-to-mars/ Experiments to seek for terrestrial-like life forms on Mars surface 1. Pyrolytic Release (PR) Experiment (Panel A) - Process: - The soil sample is exposed to radioactive carbon dioxide (14CO2) in the presence of a light source. - If photosynthetic organisms are present, they will incorporate the radioactive carbon into organic molecules. 14CO and 14CO were exposed - The sample is then heated (pyrolysis) to release any newly formed organic 2 molecules, which are detected for radioactive carbon. - Detector: Measures radioactive carbon to check if photosynthesis occurred. to soil in the presence of light 2. Labeled Release (LR) Experiment (Panel B) - Process: - The soil is mixed with a labeled nutrient medium containing radioactive organic compounds. - If heterotrophic microorganisms are present, they metabolize the nutrients and release radioactive carbon dioxide (14CO2) as a byproduct. - A detector measures the radioactive carbon in the released gases. - Detector: Detects 14CO2, indicating metabolic activity. 3. Gas Exchange (GEx) Experiment (Panel C) - Process: - The soil is first equilibrated with water vapor to simulate wet conditions. - Then, a nutrient medium (chicken soup) is added to stimulate microbial metabolism. - Any gases (e.g., oxygen, carbon dioxide, methane, etc.) produced or consumed are analyzed using a gas chromatograph. - Detector: Measures the gases to detect metabolic byproducts of heterotrophs. The Pyrolytic Release (PR) experiment (Carbon assimilation experiment) searched for evidence of photosynthesis as a sign of life. The experiment was conducted under dried conditions and in the absence of any nutrient. The Labeled Release (LR) experiment searched for evidence of heterotrophic microorganisms. In the LR experiment, a solution of water containing seven organic compounds (labelled) was added to the soil. A radiation detector in the headspace detected the presence of radioactive CO2 released during the experiment. Any carbon metabolism in the soil would be detected as organisms consumed the organics and released radioactive CO2. The Gas Exchange (GEx) experiment searched for heterotrophs, which are microorganisms capable of consuming organic material. The GEx was designed to detect any gases (Gas chromatograph) that the organisms released as a byproduct of their metabolism that would involve the uptake or release of metabolic gases. The soil was first equilibrated with water vapor and then combined with a nutrient solution(chicken soup) for 12 days. + extra document Origin of Life Where does new life come from? This question continues to engage scientists from diverse ﬁelds, including chemistry, biophysics, molecular biology, geology, astronomy and involves also other non scientific fields as religion, philosophy etc Was this a singular event of low probability to repeat itself and can new forms of life (and where) can be found? It is unlikely that any overall theory of life’s nature, emergence, and evolution can be fully formulated, quantiﬁed, and experimentally investigated. The various theories had almost no influence on one another, because they were developed in total isolation from one another 1. SPECIAL CREATION This theory posits a supernatural origin for life, a view held from Supernatural origin ancient Greece to Darwin's time (350 BC to the mid-1800s). Aristotele to Darwin, 350 BC to 1800 Proponents of special creation argue that natural processes alone are insufficient to generate life, necessitating divine intervention or external intelligence. Aristotle and later religious thinkers maintained that species are immutable, having been created in their current forms. While special creation was unchallenged for almost two millennia, evolutionary creationism emerged later, which integrates scientific knowledge with the belief that life was created by a divine force and then evolved. Theory without scientific foundation! SPECIAL CREATION ‘Natural’ processes are not capable of creating or developing life on their own, and that some outside living intelligence is necessary to produce life. Biblical fundamentalism: Immutability of species which were divinely created in their current forms, i.e since the time of creation each organism remained the same. Evolutionary creationism accepts the scientific age of the Earth and biological evolution suggesting that life was initially created and then evolved. SPECIAL CREATION ‘Natural’ processes are not capable of creating or developing life on their own, and that some outside living intelligence is necessary to produce life. Biblical fundamentalism: Immutability of species which were divinely created in their current forms, i.e since the time of creation each organism remained the same. Evolutionary creationism accepts the scientific age of the Earth and biological evolution suggesting that life was initially created and then evolved. An alternative theory that dominated early scientific thought was spontaneous generation, which proposed that life regularly arose from non-living matter. For example, flies were thought to emerge from decaying meat. This theory persisted until experiments, notably those of Francesco Redi (1668), Louis Pasteur (1859), and others, disproved it. Redi's experiment using jars with meat, some covered and some exposed, demonstrated that maggots only appeared in the uncovered jars where flies had access to lay eggs. Pasteur's famous swan-neck flask experiment further discredited spontaneous generation by showing that no microorganisms developed in sterilized broth unless exposed to dust from the air, confirming that life arises from existing life, not inanimate matter. This notion had been posited by Aristotle (382-322 B.C.) and other Greek philosophers to explain decay and appearance of animals such as flies and frogs, and was widely held as common sense even in 1700's and 1800's This theory was unchallenged (and therefore accepted) for almost 2000 years 2. SPONTANEOUS GENERATION Simple organisms emerge from inanimate materials: life comes from not life Lamarck (1809): Evolution of Life is described as progression (evolution) from simpler to more complex and advanced forms Maggots from meat Mice from sweaty shirts and wheat Maggots were developed spontaneously via recombination of matters in rotting materials. He demonstrated that maggots arise from flies and not from decaying matter and therefore life produced another life Spontaneous Generation - The hypothesis that life arises regularly from non-living thing Experiments That Helped to Disprove Spontaneous Generation A. Italian physician and poet, Francesco Redi (1668): the founder of experimental biology 1. Hypothesis: Maggots arose from tiny, non-visible eggs laid on meat 2. Procedures: a) Put pieces of meat in several jars, leaving half open to the air (experimental control) b) Cover the other half with thin gauze to prevent entrance of flies Spontaneous Generation - The hypothesis that life arises regularly from non-living thing Results of Francesco Redi experiment: a) After a few days, meat in all jars spoiled and maggots were found only on the meat in the uncovered jars One of the first documented experiments to use a control! The maggots were the offspring of flies, not the product of spontaneous generation The simpler life forms discovered with rudimental microscope visible complexity, and most people still believed these could arise spontaneously. Spontaneous Generation - The hypothesis that life arises regularly from non-living thing Lazzaro Spallanzani (1770) ◼Suspected infection from the tiny microrganisms in the air before sealing ◼Boiled broth and removed the air by completely sealing the flask ◼No microbes appeared ◼Conclusion: air had brought microbes to the broth ◼Criticism: spontaneous generation needed air and boiling the broth for long would kill the essence of life Spontaneous Generation - The hypothesis that life arises regularly from non-living thing Louis Pasteur (1859): All life forms come from pre-existing life forms The Key Experiments That Helped to Disprove Spontaneous Generation French scientist, Louis Pasteur (1859) The French Academy of Sciences held a contest for the best experiment either proving or disproving spontaneous generation 1. Hypothesis: Microorganisms do not arise from meat broth 2. Procedures: a) Place broth in a flask with a long, curved neck (This permitted air to enter, but trapped dust and other airborne particles) © 2016 Paul Billiet ODWS b) Boil the flask thoroughly to kill any microorganisms c) Do NOT seal the open end of the flask d) Wait an entire year before gathering results Spontaneous Generation - The hypothesis that life arises regularly from non-living thing Results: a) After a year, no microorganisms could be found in the broth! b) Pasteur then removed the curved neck, permitting dust and other particles to enter. In just one day, the flask contained microorganisms! c) Microorganisms had clearly entered the flask with the dust particles from the air Spontaneous Generation - The hypothesis that life arises regularly from non-living thing A critical observation Dust in the neck Although air could enter the flask, bacteria present in the air were trapped at the curve of the neck © 2016 Paul Billiet ODWS Darwin’s theory (1859) There is not necessarily a ladder of progress from simple to more complex forms ( as stated by Lamarck). Simple organisms can be as evolutionarily successful as complex ones. This allowed the idea that all life, simple and complex, had a single origin in the distant past. “If (and oh! what a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity present, that a protein compound was chemically formed, ready to undergo still more complex changes...”. -All organisms originated from a common ancestors -All organisms have and continue to change over time -Evolution or organisms began 3.7 billion ago The earliest evidence for cell-like structures dates back about 3.23 BYA Pilbara region of Western Australia and in the Barberton Mountain Land in South Africa host the oldest rocks that are sufficiently well preserved to contain fossils. These rocks contain structures that are interpreted as fossil stromatolites (formed by colonies of photosynthesizing bacteria known as cyanobacteria (blue-green algae) lived in the shallow waters) FROM: Rasmussen 2000 NATURE Stromatolites from Western Australia: Hamelin Pool Marine Nature Reserve Stromatolites are living fossils and the oldest living life forms on our planet and represent the most ancient ecosystem ABIOGENESIS CHEMICAL EVOLUTION Abiogenesis, describes the chemical processes that took place on the “prebiotic Earth” about 4500 to 3500 mya ago (prebiotic evolution). These events preceded biological evolution, a phase which led to the appearance of first “living cells” capable of self-reproduction at the expense of some rudimentary metabolism Chemical reactions on the early Earth could have led to the production of a range of organic compounds, forming a ‘primordial soup’ in which the required building blocks for life would have been present. The uniformity of biochemistry in all living organisms argues strongly that all modern organisms descend from a last- common universal ancestor (LUCA) Pre-life chemical reactions may have given rise to a living system: Non life became life (ABIOGENESIS) Abiogenesis theory is based on a naturale process callled CHEMICAL EVOLUTION CHEMICAL EVOLUTION refers to change in things that DO NOT NEED TO BE CAPABLE OF REPRODUCTION CHEMICAL EVOLUTION Basic chemistry can give rise to living cells C E refers to changes in «things» (individual molecules or entire chemical systems) that do not need to be capable of reproduction 1 2 Fatty Acids however, remain suspended in warm water, 3 growing in number as the cycle repeats. When fatty acid 4 concentrations 5 6 As fatty acid collections continue to increase, they join together to make a large skins! are high enough, they bunched together automatically self-assembling into a stable ! ball 7 8 If fluctuations in the skins happened to make the edges touch, water forces those edges the fused together. The end result is a stable hollow container similar to the membrane, or skin, of a living cell! Abiogenesis: filling the gap between chemical and biological evolution Abiogenesis: chemical reactions with abiotic inorganic molecules producing organic compounds that give rise to compounds necessary to create life. They are not who organisms by non living matter as described by the evolution theories. ABIOGENESIS CHEMICAL EVOLUTION can give rise to systems that are fully capable of reproduction CHEMICAL EVOLUTION The formation of complex organic molecules from simpler inorganic molecules through chemical reactions in the oceans during the early history of the Earth or the first step in the development of life on this planet. This idea was first proposed in the 1920s and is known as Oparin-Haldane hypothesis and was published in 1952 by the Urey-Miller experiment Life’s First Steps Carbon Ammonia The concept of chemical Monoxide evolution offers a systematic understanding of the origins of life from a chemical perspective: the chemical-beginning, Water and Activated Peptide and Volcanic Gases Acetic Acid Pyruvic Acid Alanine Water chemical-evolution, and chemical-life. Carbon Oxygen Nitrogen Sulfur Hydrogen The chemical evolution of organic molecules is represented in abiogenesis theory A blueprint describing how biomolecules may have evolved from inorganic chemicals spewing from the seafloor; with a jump-start from sulfide minerals (not shown), each step incorporates raw materials readily a vailable at hydrothermal vents to fashion a more complex molecule. Electric spark or primordial soup: Life might have evolved from non living matter (chemical evolution) The view that life emerged through a long process of chemical evolution was set forth by the Russian biochemist Alexander Oparin in 1924 and by J. B. S. Haldane in 1929 and demonstrated some years later (1953) Oparin suggested that simple molecules (e.g., CH4, NH3) in the early Earth, reacted to form small bio-molecules and later into complex bio-polymers (e.g., nucleoside, nucleotide, peptide, polynucleotide) which then evolved into multimolecular functional systems, and finally ‘life’. Simple molecules were able to form only because oxygen was absent. He pointed out that the transformation of lifeless chemicals into living matter extended over a period of almost a billion years! Oparin-Haldane Model Miller and Urey experiment (1953) demonstrated that complex organic compounds could be synthetized from simpler inorganic precursors ◼Miller and Urey (1953, University of Chigago) recreate conditions similar to those of the Early Earth in vitro ◼The water mix is heated and the mixture circulates for many days. Electrical sparks passed through a mixture of hydrogen, water, ammonia and methane simulating a thunderstorm on the primitive Earth provided energy necessary to arrange simple molecules of CH4, NH3, PO4 salts, and H2O into the basic building blocks of organic compounds Condenser simulated rain fall causing dropping of the newly formed compounds into the other flask ▪H2CO - Formaldehyde ▪HCN – Hydrogen Cyanide ▪Amino Acids ▪Urea After one week, 10-15% of the carbon had turned into organic compounds, and 2% of the carbon had created amino acids, the building blocks of proteins/life besides other organic compounds Other biologically important molecules had been formed including ethanoic acid, lactic acid and urea Later similar experiments were done using CO2 that produced nucleotides Miller experiment opened up a sub-ﬁeld of organic synthesis—non- enzymatic syntheses of biomolecules and their biopolymers under plausibly prebiotic conditions ◼These experiments cannot reproduce the exact conditions on the primitive Earth: the process they discovered was probably not representative of the emergence of life on Earth ◼BUT basic building blocks for the large macromolecules can be synthesised in vitro from inorganic compounds without enzymes NON ENZYMATIC PRIMORDIAL CHEMISTRY © 2016 Paul Billiet ODWS CHEMICAL/ARTIFICIAL SYNTHESIS OF ORGANIC MOLECULES In the early days of chemistry, it was believed that organic compounds could only be produced by living organisms. But, in 1828, Friedrich Woller (german chemist) was able to manufacture the organic compound urea under laboratory conditions. The artificial production of urea suggested that life might be powered by normal chemical reactions, which could be studied and understood. “Darwinian evolution needs informational molecules, so RNA must have come first” “You can t get by without building blocks and energy, so metabolism must have come first” “Genetics and metabolism without catalysis is hard to imagine, so proteins must have come first” “Biochemistry is too complicated to replicate from generation to generation without a reliable mechanism to pass on genetic information.” “The development of Darwinian selection is hard to imagine without compartments, so membranes must have been there at the outset” 3. PANSPERMIA (Extraterrestrial origin or cosmozoic theory) Panspermia means seeds everywhere: The “seeds” of life (molecules or even life forms) exist all over the Universe and can be propagated through space from one location to another. The german physicist H.E. Richter (1865) firstly proposes a mechanism with meteors as the transfer vehicles for life through space and may be considered the founder of the modern theory of Panspermia Lithopanspermia (interstellar panspermia) – impact-expelled rocks from a planet’s surface serve as transfer vehicles for spreading biological material from one solar system to another (Ritcher, 1865) Ballistic panspermia (interplanetary panspermia) – impact-expelled rocks from a planet’s surface serve as transfer vehicles for spreading biological material from one planet to another within the same solar system Rocks ejected experience shock deriving form the transfer and the impact range from 5- 10 GPa to 55 GPa, heating in the range from 40ºC to 350ºC and acceleration on the order of 3.8 x 106 m/sec2 (mathematical simulation). PANSPERMIA “Panspermia” theory is based on the proof that bacteria could survive a long journey withstanding with different kind of conditions including extreme vacuum, desiccation, solar and cosmic radiation, microgravity and both extreme hot and cold temperatures The discovery of Martian meteorites on Earth proved that intact rocks can be transferred between the surfaces of planetary bodies in the Solar System (the minimum Mars-Earth transfer time is only of 7 months) The analysis of Martian meteorite ALH84001 (Antarctica, 1984) showed that it was probably not heated over 40ºC since before it was ejected from Mars Experimental model: Different bacteria were tested for their ability to withstand the harsh physical conditions (among witch ultracentrifugation, hypervelocity, shock pressure and heating to simulate the physical forces that hypothetical endolithic microbes would be subjected during ejection from one planet and landing on another). Model chosen: B. subtilis spore or vegetative cells of the soil bacterium i.e. Deinococcus radiodurans some halophilic archaea (Halorubrum and Halobacterium spp.), the cyanobacterium Chroococcidiopsis and the lichens Xanthoria elegans. Results: Spaceflight experiments demonstrated that with minimal UV shielding ( i.e. 2 meters of meteors shield) several types of microbes can survive for years at exposures to the harsh environment of space and spores are estimated to survive up to 25 million years in space (solar UV is the most immediately lethal agent) Allan Hills 84001 was found in the Allan Hills in Antarctica on 1984. Its mass was 1.93 kilograms. The Earth–Mars system is not the only place where natural transfer may occur. The discovery of potentially habitable environments such as the satellites of Jupiter and Saturn (e.g. Europa, Ganymede, Callisto, Titan and Enceladus), expands the possibility of interplanetary transfer of life in the Solar System Electric spark or primordial soup: Life might have evolved from non living matter (chemical evolution) Oparin-Haldane Model Open questions: -How did different types the molecules first start working together, eventually producing the genetic code and the cell as unified entity? -What were the original reproducing creatures actually like? Were they similar to the cells we have today? Or were they something much simpler? How likely is it the life has formed or is forming, in other regions are galaxy? From where the energy necessary for the chemical synthesis of the forerunners molecules of the primeval life come from? Energy was provided mostly by ultraviolet light (UV), but also lightening (Stanley experiment), radioactivity, and heat- hydrothermal vents (hot volcanic outlets in the deep-sea floor) etc. for formation of life we need: - building blocks: chnops - energy: UV, lightning, radioactivity, vents (heat) - liquid solvent: H2O https://researchoutreach.org/articles/origin-life- conditions-sparked-life-earth/ Origin of the Earth It all started with “The Big Bang” approximately 13.8 billion years ago. The Big Bang led to an unimaginable expansion of the universe and ultimately the formation of the solar system and Earth nearly 4.5 billion years ago. In the beginning, the Earth was giant ball of molten lava in hot, gaseous form. Slowly with time, it cooled down, leading to the formation of the solid Earth’s crust. At the same time, the condensation of vapour led to great torrential rains, that fell through the atmosphere, dissolving gases and continued for thousands of years, leading to the formation of oceans and seas. The primitive ocean was different from the present ocean as it had so many organic (according to Oparin hypothesis) and inorganic compounds dissolved in It deriving also from the run-off of rainwater from the land carried dissolving minerals, well soluble salts (Na-, K+. Mg++, Ca++) into a shallow proto-ocean; hence it is also referred to as primordial soup. The prebiotic sea must have been acidic because of the high concentration of CO2 with temperature ranging from at least from 70° to 100°C or more. Some toxic molecules were probably present*. The atmosphere of primitive Earth was not like the present-day atmosphere. The gaseous content was very different. There was no gaseous oxygen in the atmosphere at all, and the atmosphere was probably reducing type. Volcanic activity released gases into the primitive atmosphere (probabily ammonia = NH3, carbon monoxide = CO, hydrogen sulfide = H2S, methane = CH4, nitrogen = N2, water vapor = H2O; a greenhouse effect mainly due to water vapour and CO2 is considered plausible) Since the present-day atmosphere is oxidising now, it is believed that gaseous oxygen is not supporting the origin of the new life forms. However, the evolution of existing life continues. H2O+XY) Every condensation reaction generates a water molecule: if life emerged in watery environments, condensation reactions would be diluting the reactant with the continued process of polymerisation Condensation reactions are chemical processes where two molecules join together, and a small molecule (often water) is released as a byproduct. Polymerization refers to the process where smaller molecules (monomers) bond together to form larger, more complex molecules (polymers), such as proteins, nucleic acids, or synthetic polymers. For condensation and polymerization reactions to happen efficiently, the precursor molecules need to be concentrated. This is because reactions tend to happen more readily when molecules are close together. In a watery environment, the water acts as a solvent, and it can dilute the concentration of these precursor molecules. As a result, the reactions needed to form complex molecules might be less likely to occur because the reactants are spread out in the water. Theoretically, the process of polymerization could create more water while also relying on water to drive the reactions. If life originated in a watery environment, this creates a problem: as condensation reactions occur, the reactants would get more diluted, making it harder for polymerization (and therefore the formation of complex molecules) to proceed efficiently. From where the energy necessary for the chemical synthesis of the forerunners molecules of the primeval life come from? Energy was provided mostly by ultraviolet light (UV), but also lightening (Stanley experiment), radioactivity, and heat- hydrothermal vents (hot volcanic outlets in the deep-sea floor) etc. https://researchoutreach.org/articles/origin-life- conditions-sparked-life-earth/ Where did life begin? Land? No O2, no ozone: UV destroys molecular bonds Shallow ponds? Once favored, full of organic material When evaporated, organic chemical concentration increases making it easier to combine complex molecules leading to life Impacts form heavy late bombardament might have destroyed life near the surface while allowing it to be preserved deep in the oceans or within the Earth’s crust lack of chemical energy sufficient to support life? Deep-sea vents/hot springs? Early organisms might have survived in conditions similar to deep-sea vents Plenty of chemical energy available Chilly start? ice layer protects from impact, uv and more stable in cold env Ice protects labile molecules from degradation and increases concentration Tidal pools: cycle of evaporation, condensation, etc. (cooling and warming of water). ALSO in the past the moon was much closer to Earth when it formed. So there were more tidal fluctuations. So more and frequent and strong cycles of warming and cooling. …..or under the ice covering the primitive ocean. According to some solar evolution models, the sun was some 30 percent dimmer at that time, providing less heat to Earth. So as soon as the hail of asteroids stopped, Earth may have cooled to an average surface temperature of –40°F and a crust of ice as much as 1,000 feet thick may have covered the oceans. Approaching the problem of origin of life from physics point of view Our universe is prone to disorder and chaos, so how did it generate the extreme complexity of the living forms? Particles that make up any system all have some degree of random motion that tends to drive the system towards a disordered arrangement which is a high entropy state*. According to second law of thermodynamics, a closed system will only increase in entropy: however Life seems to resist the second law of thermodynamics and maintains low entropy (its structure is extremely specific and non-random )* Why life only apparently contradicts the second law? (1) The second law tell us that closed systems (unable to exchange energy/matter with the outside environment) must increase in entropy. But living organisms and indeed the Earth's biosphere are not closed since receive energy from outside (source of energy come from the sun) Life acts to reduce its own internal entropy by increasing the entropy of its surroundings Life absorbs (feeds on) order and it ejects disorder into its surroundings. Life feeds on the special out-of-equilibrium energy sources i.e. on energy gradients* The importance of energy gradients to life can help us understand the actual origin of life and its precursors There are a few hypotheses on the location of the very first forms of life: tidal pools, around deep sea hydrothermal vents or on the undersurface of Earth's ice caps*. These environments share a common property: they sit at persistent energy gradients struggling to return to equilibrium, obeying the second law of thermodynamics by redistributing their energy as evenly and randomly as they can. Glucose oxidation: example of entropy increase in biological systems The order produced by cells during their growth and division is more than offset by the disorder they create in the surrounding environment Why life only apparently contradicts the second law?(2) Energy can be distributed into chemical bonds of newly formed molecules : as those molecules form, new channels open up for distributing energy into the chemical bonds of increasingly complex molecules until the system reaches a thermal equilibrium. If energy source is flowing into a much larger reservoir, such as an ocean, then equilibrium is never reached. Complexity can increase indefinitely as a byproduct of the system striving to redistribute the endless gradient in energy*. Molecules better at that process become more abundant, and at some point, they become true self-replicators and eventually, they become life. Schema of the Oparin’s Bubble Hypothesis Mimicking the atmosphere Water vapor produced by boiling the main flask simulated Condenser simulated rain fall evaporation from causing dropping of the newly the oceans formed compounds in the form of rain back into the other flask ▪H2CO - Formaldehyde ▪HCN – Hydrogen Cyanide ▪Amino Acids ▪Urea Bubble hypothesis for the evolution of life by chemical processes at the ocean edge. Various versions of the bubble theories have been proposed by different scientists depending on the composition whether the bubbles are lipid or protein based and how there as synthesized. The most accepted bubble proposal is the lipid based bubbles called coacervates. The chemistry of life is the chemistry of reduced organic compounds, and therefore all theories for the origin of life must offer testable hypotheses to account for the source of these compounds. The best-known theories for the origin of organic compounds are based on the notion of an ‘organic soup’ that was generated either by lightning-driven reactions in the early atmosphere of the Earth or by delivery of organic compounds to the Earth from space When submarine hydrothermal vents were discovered 40 years ago, hypotheses on the source of life’s reduced carbon started to change. These vents harbour rich ecosystems, the energy source of which stems mainly from mid-ocean-ridge volcanism Synthesis of amino acids is just a first step. In 1964, Sidney Fox heated a mixture of 18 amino acids to temperatures of 160-200ºC. for varying periods of time. He obtained stable, protein-like macromolecules termed Coacervates. These aggregates grew up and bud off to make more Coacervates are not living cells, but their might represent a way in which the first cell may have formed The protein complexes surrounded themselves with a watery shell which allowed the inside to differ from the outside environment As coacervates became more complex they may have developed biochemical systems with the capacity to release energy from organic nutrients in the “Hot Thin Soup”. The first cells were heterotrophs according to Oparin When the proteinoid material was cooled and examined under a microscope, Fox observed small, spherical units that had arisen from proteinoid aggregations. These microspheres showed a general resemblance to simple bacteria. Reducing Atmosphere of the early Earth The primitive atmosphere was not conducive to life Energy sources such as solar energy, UV rays, gamma rays, lightening, radiation from the earth were much greater than today and were the energy sources for chemical reactions between gases (no ozone layer) Early atmosphere is often referred to as a reducing atmosphere. ▪ Oparin thought that there was methane (CH4), water vapor (H2O), Hydrogen gas (H2), and ammonia (NH4) ▪ Ample availability of hydrogen, carbon, and nitrogen atoms ▪ very little free oxygen (O2) (If free oxygen had been there- life would not have evolved) ▪ As energy hit the molecules in the early atmosphere bonds broke and new ones were made. ▪ The ocean became a “hot thin soup” filled with organic molecules. ▪ The Earth’s surface temperature probably hotter than today. The atmosphere of the primitive earth was rich in hydrogen, both in the elemental state and united with carbon in methane, with nitrogen to form ammonia, and with oxygen as water vapor. Does the biochemistry of modern cells offer any insight into its own origins? can studying the chemical processes and molecules in current living cells reveal anything about how life originally began. Can we trace certain biochemical pathways or molecules back to simpler, earlier forms? Can modern cell chemistry help reconstruct the transition from non-living chemistry to living systems? This asks whether we can match the development of life's early chemistry Can we seek for congruence between the (biochemistry) with specific conditions on early Earth, such as: Hydrothermal vents (hot, mineral-rich environments at the ocean floor), Volcanic environments, Shallow origins of biochemistry and particular early pools of water rich in organic compounds. The idea is to find a link between: "Where life’s chemistry might have started" Earth environments? and "The natural conditions that could have facilitated it." The ﬁrst biological catalysts have been selected in the context of protometabolism, meaning that they enhanced a process that occurred spontaneously, driven by natural disequilibria and catalysed by inorganic catalysts Biological catalysts(enzymes) in modern cells speed up reactions that are vital for life. Before life existed, protometabolism refers to a primitive set of chemical reactions that happened spontaneously in the environment, not in cells. In this prebiotic (before life) stage, Natural disequilibria (differences in temperature, pressure, or chemical concentrations) drove chemical reactions AND Inorganic catalysts (like minerals) A proto-metabolism is a series of linked chemical enhanced these reactions. reactions in a prebiotic environment The first that preceded and eventually turned into modern biological catalysts likely evolved to enhance these pre-existing reactions, metabolism. making them more efficient or specific. Hydrothermal vent represent a vast domain of chemistry They are geochemically reactive environments that might have supplied suitable conditions for sustained prebiotic syntheses The ultra-mafic underpinnings of the Lost City system have a similar chemical composition to lavas that erupted into the primordial oceans on early Earth. Consequently, the LCHF provides insights into past mantle geochemistry and presents a better understanding of the chemical constraints that existed during the evolutionary transition from geochemical to biochemical processes. Global distribution of sea-floor hydrothermal vents Deep sea vents have been identified in many location along mid-ocean ridges and along the flanks of undersea volcanoes Black smoker systems are fueled by volcanoes and emit chemically modified sea water “Black smokers” are Black smokers are chimneys formed from located directly deposits of iron sulfide, above magma which is black. chambers “White smokers” are chimneys formed from deposits of barium, calcium, and silicon, which are white. Beneath the fissured sea-floor, sea-water seeps through cracks and comes into close contact with the magma chamber during its circulation from the ocean floor, before moving through the crust to re-emerge at the vents. The hot water is too much under pressure to boil and erupts as smoky fountains and contain hot (350°C) acidic (pH 2-3) dissolved sulfide minerals rich in transition metal such as Fe(II) and Mn(II). When they encounter the near-freezing seawater they precipitate forming chimney-like structures. They also contain CH4, magmatic CO2, dissolved H2 Dark plumes of water and irregular deposits (including “chimneys”) on the seabed This black smoker is one of the many active hydrothermal vents located in the Galápagos © NOAA Photo Library via Flickr (CC BY 2.0) https://www.youtube.com/watch?v=fOGEuhQPKvY Microbially Mediated Hydrogen Cycling in Deep-Sea Hydrothermal Vents Frontiers in Microbiology, https://doi.org/10.3389/fmicb.2018.02873 The rich supply of nutrients support chemotrophic bacteria (feeding on sulfur compounds) that support a complete food web of seafloor creatures, including tube worms, arthropods, fish, and other benthic life forms adapted to these harsh and temporary environments. Strain 121 (Geogemma barossii) isolated from Mothra hydrothermal field in North-East Pacific Ocean Strain 121 Scientific classification Domain: Archaea Phylum: Thermoproteota Class: Thermoprotei Order: Desulfurococcales Family: Pyrodictiaceae Genus: Geogemma Species: Geogemma barossii The dissolved gases and metals in black smokers fuel the microbial communities that serve as the base of the food chain in these ecosystems. Some of the archaea in black smokers can replicate at temperatures up to 121°C, which is currently thought to be the upper temperature limit of life. https://oceantoday.noaa.gov/underwatervolcanoes/ Schematic illustrating the geological, hydrothermal, chemical and biological relationships within the Lost City Hydrothermal Field. Fluids migrating into the massif interact with olivine-rich ultramafic rocks at temperatures up to 200°C. This process results in the generation of pH 9-11 fluids, rich in methane, hydrogen and hydrocarbons and almost no CO2. Aragonite, calcite and brucite are deposited to form chimneys as the metal-poor, 40-91°C hydrothermal fluids mix with cold seawater. The warm porous interiors of the chimneys host dense biofilms dominated by a single phlyotype related to Methanosarcinales (methane proucer) City lost is located at Atlantis Massif, i.e. at the intersection between the Mid-Atlantic Ridge and the Atlantis Transform Fault, in the Atlantic Ocean: carbonate towers up to 60 meters high Sea water invades the warm oceanic crust through cracks and the exhalate has circulated through the crust, where it can be heated up to ~200°C, but their waters do not come into close contact with the magma chamber as for black smokers https://www.youtube.com/w atch?v=BFExaMByzYw https://www.youtube.com/watch?v=ffWvsHkPLpY Hydrothermal Alkaline vents are highly stable geological systems:Lost city is estimated to be about 100,000-years old Mineral rich in magnesium, iron and silicate Lost City venting is the consequence of a process called serpentinization, the exothermic reaction of ultramaﬁc minerals (igneous rocks that contain magnesium and iron from the upper mantle, in particular olivine) with water. These rocks have different compositions compared with those of submarine volcanoes, because they are dominated by the magnesium- and iron-rich mineral olivine*. This reaction produces large volumes of H2 and methane dissolved in warm (45–90 °C) alkaline (pH 9–11) ﬂuids containing magnesium hydroxides and where CO2 is almost absent. Alkaline vents do not form chimneys, as in black smokers (and indeed do not normally ‘smoke’ at all) but rather are labyrinthine networks of interconnected micropores bounded by thin inorganic walls containing catalytic Fe(Ni)S minerals, through which H2-rich hydrothermal ﬂuids (and ocean waters) percolate. Lost city is about 30000 years old! Alkaline hydrothermal vents Micropores are tiny, interconnected pores found within certain geological formations, such as rocks and sediments. They typically have diameters less than 2 nanometers. In the context of alkaline hydrothermal systems, these micropores are significant because they create a network that allows for fluid movement and chemical exchanges between the vent fluids and the surrounding rocks. The "thin inorganic barriers" refer to the materials that separate the vent fluids from the surrounding environment, which can include minerals and solid geological formations.These barriers are crucial for maintaining distinct chemical environments, as they allow for the formation of proton gradients. A proton gradient occurs when there is a differenceThe Lost City vent field is characterized by carbonate towers up to 60 m in proton concentration across a membrane or in height made up by the mixing of warm high pH fluids with sea-water barrier. In alkaline hydrothermal systems, this gradient is essential for various that causes carbonate precipitation and the growth of chimneys. geochemical processes. The natural proton gradient generated across the inorganic barriers helps drive several chemical reactions and influences the biological activity in the vent environment. The white deposits here Seawater-basalt reactions driving volcanically hosted vents produce are typically composed of mineral precipitates, which can form as a result substantial amounts of CO , sulfide in the millimolar range, and low pH 2 of the interaction between vent fluids and the (3 to 5), as well as extremely high temperatures (200° to 400°C). In surrounding seawater. Common minerals that contrast, the Lost City vents have very low CO2 concentration but form these deposits include calcium carbonate provide high fluxes of hydrogen and methane at warm temperatures (CaCO3) and silica (SiO2) The specific conditions, (40° to 90°C) and high pH (9 to 11). such as temperature, pH, and concentration of dissolved ions, determine the types of minerals that precipitate. As alkaline hydrothermal fluids rise from the ocean floor, they mix with the cold seawater. This interaction can lead to changes in temperature and pressure, causing dissolved minerals to precipitate out of the solution and form solid deposits.The presence of microorganisms can also play a role in the formation of these deposits by promoting the precipitation of minerals through biological processes. *The ultramafic underpinnings of the Lost City system have a similar chemical composition to lavas that erupted into the primordial oceans on early Earth. Consequently, the LCHF provides understanding of the evolutionary transition from geochemical to biochemical processes*. Alkaline hydrothermal systems sustain natural proton gradients across the thin inorganic barriers of interconnected micropores within deep-sea vents Could abiotic vent chemistry preﬁgure the origins of biochemistry and metabolism? Alkaline hydrothermal systems are appealing because of their resemblance to the core energy metabolic reactions of some modern prokaryotic autotrophs Alkaline hydrothermal systems sustain natural proton gradients across the thin inorganic barriers of interconnected micropores within deep-sea vents. In Hadean oceans, these inorganic barriers should have contained catalytic Fe(Ni)S minerals similar in structure to cofactors in modern metabolic enzymes, suggesting a possible abiotic origin of chemiosmotic coupling. Chemiosmotic coupling is universal: in all known autotrophic bacteria and archaea, carbon and energy metabolism is driven by electrochemical ion (generally proton) gradients across membranes. It must have arosen very early in evolution*. The continuous supply of H2 and CO2 from vent ﬂuids and early oceans, respectively, offers further parallels with the biochemistry of ancient autotrophic cells, i.e the acetyl CoA pathway in archaea and bacteria*. Reactor, describing the precipitation of thin-walled, inorganic structures containing nickel-doped mackinawite, a catalytic Fe(Ni)S mineral, under prebiotic ocean conditions simulating vent structures Alkaline hydothermmal vents are the higher the concentration of atomic electrochemical reactors hydrogen the lower the pH, the more acidic The surrounding The vent fluid is hot it is seawater on the alkaline and it has high other hand is cold levels of dissolved acidic and has high molecular hydrogen levels of dissolved carbon dioxide The fluid flowing out the vent is divided by the sea water by a thin layer of iron nickel sulfide rich medium which has crystallized forming the vent chimney Alkaline hydothermmal vents are electrochemical reactors The differences in the vent fluid composition and the surrounding ocen water creates an electrochemical reactor in which H2 and CO2 can react. The H2 serves as reductant, doning electrons to carbon dioxide. The iron mineral layer act as a semiconductor, shuttling electrons across the interface. The reduction of CO2 leads to formic acid which is the starting point for the creation of organic molecules. The model suggests that on meeting at the vent–ocean interface, the reaction between H2 and CO2 would have produced hydrocarbons, which would in turn take roles in the transition from geochemistry to biochemistry Assisted by Fe(Ni)S minerals precipitated at the interface, a pH gradient of more than three units should have been enough to increase the viability of the reaction thereby rendering it thermodynamically favorable The higher CO2 concentration in Hadean oceans should have increased carbon availability and lowered the pH of the oceans, probably to around pH 5–7. That could have produced pH gradients of 5 or 6 pH units between the alkaline hydrothermal ﬂuids and acidic oceans while mixing could prevent such steep gradients being juxtaposed across single barriers, *Laminar ﬂow in elongated hydrothermal pores does make it feasible for sharp gradients of several pH units to exist across distances of a few micrometres, promoting organic synthesis by lowering the energetic barrier to CO2 reduction. Standars reduction potential of H2 and CO2 Whenever protons are involved in a reduction, the reduction potential depends on pH. Steep natural proton gradients across thin catalytic Fe(Ni)S barriers could theoretically promote organic synthesis by lowering the energetic barrier to CO2 reduction to CO, HCOO- and even HCHO. An Origin-of-Life Reactor to Simulate Alkaline Hydrothermal Vents Feasibility of spatially separated yet electrically coupled geochemical reactions as drivers of otherwise endergonic processes* Nick Lane, a biochemist at University College London in the UK, recreated prebiotic geo-electrochemical systems with his origins of life reactor demonstrating that alkaline hydrothermal vents have the potential to drive the origins of biochemistry from H2 and CO2 using natural proton gradients and Fe(Ni)S minerals, in a manner remarkably analogous to the acetyl CoA pathway The Acetyl CoA (Wood–Ljungdahl) pathway* Under standard conditions, the reaction between CO2 and H2 to The reduction of CO2 via H2 oxidation, produce formate (HCOO–) is facilitated by geologically sustained pH thermodynamically disfavored, gradients, would be an abiotic with ΔG0’ = +3.5 kJ mol–1 (13, analog—and evolutionary 14). Archaea and Bacteria use a predecessor—of the Wood–Ljungdahl chemiosmotic pH gradient across acetyl-CoA pathway of modern the cell membrane to power the archaea and bacteria. otherwise unfavorable step Among the known pathways of carbo

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