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

いくつかの仮説の一つは、最も古い生命形態が海底の熱水噴出口から起源した可能性を示唆しています。熱水噴出孔は熱、化学勾配、水素や硫化水素などの無機化合物を供給していました。この環境は、アミノ酸、脂質、ヌクレオチドなどの有機分子の非生物的合成を促進した可能性があります。熱水噴出孔構造内の鉱物孔は、最初の生物的区画として機能し、これらの分子を濃縮し、化学反応のために集めた可能性があります。一部のモデルでは、プロトセルは脂質膜が形成され、最終的にミネラルベースの区画に取って代わられたと示唆しています。これらの細胞は自己複製RNAを含んでおり、遺伝情報を保存しタンパク質合成を触媒する能力があったと考えられます。タンパク質が出現するにつれて、RNAとの相互作用がより安定した遺伝物質であるDNAへの移行を促したと考えられます。代謝的には、初期の細胞はおそらく化学的栄養素で、水素を電子供与体として、硫黄や二酸化炭素を電子受容体として用いて有機化合物を合成していました。

細胞生命の起源

地球上の生命の起源は、古代の生化学的プロセスと地質条件に根ざした複雑で謎めいた出来事です。実験的証拠は、生命が初期地球条件下でRNAヌクレオチド、アミノ酸、脂質などの有機分子が自然発生的に形成されたことから始まったという仮説を支持しています。火山活動、強い紫外線、自由酸素のない還元大気などの要因がこれらの反応を促進したと考えられます。海底の熱水噴出孔は最初の生命体の発生地と考えられており、水素(H₂)や硫化水素(H₂S)などの還元気体を供給し、プレバイオティック化学を促進します。鉱物孔は反応物を濃縮する閉鎖空間を提供し、外洋では分子が非常に希釈されるのとは異なります。また、鉄や硫黄が豊富な鉱物表面は原始的な触媒として機能します。これらの表面は分子同士を密接に接触させ、反応に必要なエネルギーを下げることで化学反応を加速させた可能性があります。RNAは遺伝情報を保存し、生化学反応を触媒する能力から、幼少期に中心的な役割を果たしたと考えられています。リボザイムはRNAが酵素様機能を果たせることを示し、タンパク質ベースの酵素進化前の妥当な中間段階を提供します。DNA、RNA、タンパク質の最終的な出現は、すべての現代生物に共通する三部分子構造の基盤を築きました。最後の普遍共通祖先(LUCA)はおよそ38億年から37億年前に生きていたと推定されており、細菌と古細菌の分岐を示していますが、正確な時期は不確かです。初期の細胞生命は地球の無酸素環境で代謝的に多様化しました。原始的な自養生物はCO₂を炭素源として利用し、しばしばH₂をエネルギー供給源として利用していました。窒素固定の進化は代謝の可能性を広げ、硫黄系エネルギー経路は追加のエクサーゴン反応を提供したと考えられます。水素駆動の化学栄養はCO₂からの有機分子の合成を可能にし、ますます複雑な生態系を支えました。時が経つにつれ、酸素光合成の登場を含む微生物の革新が地球の大気を変革し、最終的には好気生命の出現を可能にしました。

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

JoVE Core

Microbiology

微生物学

Unit

ユニット

Microbial Evolution

微生物の進化

KEY TERMS AND CONCEPTS

主要用語と概念

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

Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly ...

Soil Microbial Ecology

Soil microbial ecology is defined by highly diverse, spatially structured communities that drive nutrient cycling, organic matter turnover, and overall ...

Acid Mine Drainage

Mining activities that disturb sulfide-rich rocks, particularly those containing pyrite (FeS&#8322;), initiate a cascade of geochemical and ...

Microbial Corrosion

Microbiologically Influenced Corrosion (MIC) is a significant form of material degradation caused by the metabolic activities of microorganisms. This ...

Microbial Bioremediation of Hydrocarbons

Bioremediation is an environmentally sustainable process that employs living organisms&#8212;primarily microorganisms&#8212;to degrade or neutralize ...

analysis-of-earthworm-populations-in-soil

Analysis of Earthworm Populations in Soil

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
Using mustard, Lumbricus terrestris earthworm populations can be sampled ...

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.

Ecological Disturbance

An ecological disturbance is a temporary disruption in the environment resulting from abiotic, biotic, or anthropogenic factors, causing a pronounced ...

Investigation of Disease Outbreaks

Multistate foodborne outbreaks pose significant public health risks and require meticulous investigation to identify sources and implement control ...

Biodeterioration

Biodeterioration refers to the unwanted alteration of materials caused by microorganisms&#8212;especially fungi&#8212;which damage both organic substrates ...

Igneous Volcanic Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
Igneous rocks are the products of cooling and crystallization of magma. Volcanic rocks ...

applications-of-gis-disaster-management-and-emergency-response

Applications of GIS: Disaster Management and Emergency Response

Geographic Information System (GIS) technology is essential for risk identification, action prioritization, and resource optimization in critical ...

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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