Name: how early cells got their start
Uploaded: 2026-03-12T13:57:39.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Environmental Science

Earth's Systems

9-12.EVS.3.4

Origin of Cellular Life

L’une des nombreuses hypothèses suggère que les formes de vie les plus anciennes proviennent probablement des sources hydrothermales au fond de l’océan.Les sources hydrothermales fournissaient de la chaleur, des gradients chimiques et des composés inorganiques, tels que l’hydrogène et le sulfure d’hydrogène. Cet environnement aurait pu faciliter la synthèse abiotique de molécules organiques, y compris les acides aminés, les lipides et les nucléotides.Les pores minéraux à l’intérieur des structures de sources hydrothermales auraient pu servir de premiers compartiments biologiques, concentrant ces molécules et les rassemblant pour des réactions chimiques.Certains modèles suggèrent que les protocellules sont apparues lors de la formation des membranes lipidiques, remplaçant finalement les compartiments minéraux.Ces cellules contenaient probablement de l’ARN auto-réplicatif, capable de stocker des informations génétiques et de catalyser la synthèse des protéines.À mesure que les protéines émergent, leurs interactions avec l’ARN ont probablement favorisé la transition vers l’ADN, un matériau génétique plus stable.Métaboliquement, les premières cellules étaient probablement des chimiolithotrophes, utilisant l’hydrogène comme donneur d’électrons, et le soufre ou le dioxyde de carbone comme accepteurs d’électrons pour synthétiser des composés organiques.

origine de la vie cellulaire

L’origine de la vie sur Terre est un événement complexe et énigmatique, enraciné dans d’anciens processus biochimiques et des conditions géologiques. Les preuves expérimentales soutiennent l’hypothèse selon laquelle la vie a commencé par la formation spontanée de molécules organiques telles que les nucléotides d’ARN, les acides aminés et les lipides dans les conditions terrestres primitives. Des facteurs tels que l’activité volcanique, les rayonnements UV intenses et une atmosphère réduite sans oxygène libre ont probablement facilité ces réactions. Les sources hydrothermales au fond de l’océan sont considérées comme un site probable pour les premières formes de vie, car elles pourraient fournir des gaz réduits comme l’hydrogène (H₂) et le sulfure d’hydrogène (H₂S), facilitant ainsi la chimie prébiotique. Les pores minéraux offrent des espaces confinés qui concentrent les réactifs, contrairement à l’océan ouvert où les molécules seraient fortement diluées. De plus, les surfaces minérales — souvent riches en fer et en soufre — peuvent agir comme des catalyseurs primitifs. Ces surfaces ont peut-être permis d’accélérer les réactions chimiques en mettant les molécules en contact étroit et en réduisant l’énergie nécessaire à la réalisation des réactions.On pense que l’ARN a joué un rôle central dans la jeunesse en raison de sa capacité à stocker des informations génétiques et à catalyser des réactions biochimiques. Les ribozymes démontrent que l’ARN peut remplir des fonctions similaires à celles des enzymes, offrant un stade intermédiaire plausible avant l’évolution des enzymes à base de protéines. L’émergence finale de l’ADN, de l’ARN et des protéines a posé les bases de l’architecture moléculaire tripartite partagée par tous les organismes modernes. Le dernier ancêtre commun universel (LUCA) est estimé avoir vécu il y a environ 3,8 à 3,7 milliards d’années, marquant la divergence entre les bactéries et les archées, bien que le moment exact reste incertain.La vie cellulaire primitive s’est diversifiée métaboliquement dans l’environnement anoxique de la Terre. Les autotrophes primitifs utilisaient le CO₂ comme source de carbone, s’appuyant souvent sur le H₂ comme donneur d’énergie. L’évolution de la fixation de l’azote a élargi les possibilités métaboliques, tandis que les voies énergétiques à base de soufre ont probablement fourni des réactions exergoniques supplémentaires. La chimiolythrophie alimentée par l’hydrogène a permis la synthèse de molécules organiques à partir de CO₂, soutenant des écosystèmes de plus en plus complexes. Au fil du temps, les innovations microbiennes — y compris l’avènement de la photosynthèse oxygénique — ont transformé l’atmosphère terrestre, permettant finalement l’essor de la vie aérobie.

Origine de la vie cellulaire

The origin of life on Earth is a complex and enigmatic event rooted in ancient biochemical processes and geological conditions. Experimental evidence ...

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Education

Enseignement

JoVE Core

Microbiology

Microbiologie

Unit

Unité

Microbial Evolution

Évolution microbienne

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

how early cells got their start

Early cellular life began under the harsh conditions of early Earth, where simple chemicals could form more complex organic molecules. Experimental evidence supports the idea that RNA nucleotides, amino acids, and lipids could arise spontaneously in this environment. Volcanic activity, strong UV radiation, and an atmosphere with little or no free oxygen likely helped drive these reactions.

Hydrothermal vents on the ocean floor are considered one likely setting for the first life forms. These vents could supply reduced gases such as hydrogen and hydrogen sulfide, which support prebiotic chemistry, or chemistry that happens before life exists. Mineral pores would have trapped molecules in small spaces, so reactants were less diluted than they would be in the open ocean.

Mineral surfaces may also have helped early reactions. Many of these surfaces are rich in iron and sulfur, and they can act as primitive catalysts. A catalyst speeds up a reaction by lowering the energy needed and by bringing molecules close together.

RNA likely played a major role in early life because it can store genetic information and also help carry out chemical reactions. RNA molecules that act like enzymes are called ribozymes, and they show how RNA could have worked before protein enzymes evolved. Over time, DNA, RNA, and proteins formed the basic molecular system shared by modern organisms.

Scientists estimate that the last universal common ancestor, or LUCA, lived about 3.8 to 3.7 billion years ago. This was the point at which Bacteria and Archaea began to diverge, although the exact timing is still uncertain. Early cells then diversified in Earth’s oxygen-free environment.

Primitive autotrophs used carbon dioxide as a carbon source and often depended on hydrogen as an energy donor. Later, nitrogen fixation expanded the kinds of metabolism that were possible. Sulfur-based energy pathways also likely provided useful energy, and hydrogen-driven chemolithotrophy helped cells make organic molecules from carbon dioxide. Over time, microbial innovations, including oxygenic photosynthesis, changed Earth’s atmosphere and made aerobic life possible.

How Early Cells Got Their Start

origin of cellular life

Early cellular life began under the harsh conditions of early Earth, where simple chemicals could form more complex organic molecules. Experimental evidence supports the idea that RNA nucleotides, amino acids, and lipids could arise spontaneously in this environment. Volcanic activity, strong UV radiation, and an atmosphere with little or no free oxygen likely helped drive these reactions. Hydrothermal vents on the ocean floor are considered one likely setting for the first life forms. These...

origin of photosynthesis

How Photosynthesis Changed Earth

Photosynthesis changed Earth’s atmosphere and made complex life possible. It began about 3.4 to 3.8 billion years ago, when the first photosynthetic organisms used light energy to build organic compounds. These early organisms were anoxygenic phototrophs, which means they made food from light but did not release oxygen. Early photosynthesis used hydrogen sulfide (H2S) or ferrous iron (Fe2+) as electron donors instead of water. Because of that, it did not produce molecular oxygen (O2) as a...

evolutionary processes in microbes

How Microbes Gain New Traits

Microbes gain new traits through fast genetic change. Their short generation times help evolution happen quickly. Mutation, horizontal gene transfer, recombination, and genetic drift all contribute to this process. Together, these mechanisms help microbial populations adjust to changing environments. Horizontal gene transfer, or HGT, moves genes between different species. It happens in three main ways: conjugation, transformation, and transduction. Conjugation requires direct cell-to-cell...

evolution of new traits in microbes

Microbial Adaptation in Changing Environments

Microbial adaptation in changing environments can happen very quickly. Microorganisms often evolve fast because they have large population sizes and short generation times. In the lab, these changes can sometimes be measured within days. Natural selection acts on standing genetic variation, which is the genetic diversity already present in a population. When conditions change, helpful traits can be kept and increased because they improve fitness. This lets microbes respond to new pressures...

evolution of microbial genome

Microbial Core and Pan-Genome Changes

Microbial genomes change through gene gain and gene loss. These changes help microbes adapt to new environments and to other organisms they live with. In many species, genome evolution is fast and ongoing. A key idea is the difference between the core genome and the pan-genome. The core genome is the set of genes shared by all sampled strains of a species. These genes support basic cell functions. For example, Salmonella enterica has about 2,800 core genes, although the exact number can change...

microbial phylogeny

Reading Microbial Family Trees

Reading microbial family trees helps scientists study how microorganisms are related. These trees are important in microbial ecology and taxonomy. They use molecular sequences such as DNA, RNA, or proteins to compare bacteria and archaea and trace genetic changes over time. A phylogenetic tree has tips, branches, and nodes. The tips are the species that are sampled or still alive. The branches show evolutionary paths, and branch length reflects the number of genetic changes between nodes.

phylogenetic species concept in microbiology

phylogenetic-species-concept-in-microbiology

How DNA Defines Microbial Species

The phylogenetic species concept helps define microbial species by looking at DNA and evolutionary relatedness. It focuses on shared ancestry and genetic traits that can be diagnosed in different organisms. This approach is especially useful in microbiology, where other species concepts often do not work well. Traditional morphological and biological species concepts rely on body form or reproduction. Those methods can fall short for microbes because many reproduce asexually, show little...

key terms and concepts

Explore how early cells may have formed on Earth, from RNA and hydrothermal vents to LUCA, early metabolism, and the rise of oxygenic photosynthesis.

How Early Cells Got Their Start | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Origin of Photosynthesis

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Microbial Corrosion

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Analysis of Earthworm Populations in Soil

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What is an Ecosystem?

Overview

An ecosystem is the interaction between all abiotic and biotic factors in an environment and can be classified as terrestrial or aquatic. ...

4. Engage in an evidence-based argument to explain how Earth's systems affect the biosphere and the biosphere affects Earth's systems over various amounts of time. Examples: Use data to make a claim that microbial life increases the formation of soil or that corals create reefs and argue that these processes can alter patterns of erosion and deposition along coastlines. Clarification: This discussion should consider Earth's geological history.

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Igneous Volcanic Rock

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5. Obtain, evaluate, and communicate information regarding how short-term and long-term natural cyclic fluctuations cause ecosystem change. Examples: Explain how the eruption of volcanoes alters global temperatures or how the El Niño-Southern Oscillation shifts weather patterns. Share information regarding how forest fires can cause deforestation which increases water runoff and soil erosion. Describe how hurricanes destroy dunes and increase coastal flooding.

9-12.EVS.3.5

How Early Cells Got Their Start

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