Name: microbial core and pan-genome changes
Uploaded: 2026-03-12T13:57:40.000Z
Duration: 1 min 8 s
Channel: JoVE

Les génomes microbiens évoluent au fil du temps par l’acquisition et la perte de gènes.Au sein d’une espèce, plusieurs souches héritent systématiquement d’un ensemble commun de gènes appelé génome central.Par exemple, on estime que l’espèce bactérienne X possède environ 5 familles de gènes de base partagées entre les souches analysées.De plus, certaines souches peuvent acquérir des gènes supplémentaires, souvent par transfert horizontal de gènes.Le pangénome de l’espèce X est formé par l’ensemble complet des familles de gènes principales présentes dans les souches étudiées, ainsi que par les gènes supplémentaires présents dans de nombreuses souches.Chez certaines espèces, le pangénome s’étend continuellement à mesure que de nouveaux ensembles de gènes sont acquis.Ces gènes acquis peuvent être neutres voire nuisibles, entraînant des délétions génétiques courantes dans les génomes microbiens, tandis que la sélection naturelle conserve les gènes bénéfiques.Ainsi, tous les gènes de la survie de base font partie du génome central d’une espèce.

Évolution du génome microbien

L’évolution du génome microbien est un processus hautement dynamique façonné par le gain et la perte continus de gènes à travers les espèces et les souches. Cette flexibilité génomique permet aux micro-organismes de s’adapter rapidement aux pressions environnementales et aux interactions avec d’autres organismes. La distinction entre le génome central et le génome de Pan est au cœur de la compréhension de cette diversité.Le génome central comprend les gènes partagés par toutes les souches échantillonnées d’une espèce, représentant des fonctions essentielles nécessaires aux processus cellulaires fondamentaux. Par exemple, on estime que Salmonella enterica contient environ 2 800 gènes centraux, bien que ce nombre varie selon les souches analysées. En revanche, le pangénome inclut tous les gènes présents sur toutes les souches, incorporant à la fois des gènes de base et spécifiques à la souche. Certains sérovars, tels que S. enterica Typhimurium, contribuent à des gènes uniques qui élargissent le pangénome de l’espèce.Le transfert horizontal de gènes (HGT) est un moteur majeur de l’acquisition des gènes, introduisant de nouveaux traits permettant aux microbes de résister aux antibiotiques, d’occuper de nouveaux créneaux ou de métaboliser de nouveaux substrats. Cependant, de nombreux gènes acquis n’apportent aucun bénéfice et peuvent être éliminés par délétions génomiques ou dérive génétique, contribuant à maintenir des génomes rationalisés dans de nombreuses lignées microbiennes. Parallèlement, certains microbes subissent une expansion génétique lorsque leurs niches écologiques exigent des capacités métaboliques plus larges.La génomique comparative a révélé que tous les génomes bactériens et archéens partagent un petit ensemble d’environ 30 à 60 familles de gènes universellement conservées. Ces gènes codent des fonctions fondamentales telles que la réplication de l’ADN, la transcription, la traduction et les voies métaboliques de base, reflétant des contraintes évolutives profondes.Ensemble, l’acquisition, la perte et la rétention sélective des gènes illustrent comment les génomes microbiens restent à la fois remarquablement adaptables et fondamentalement contraints par des exigences biologiques essentielles.

Microbial genome evolution is a highly dynamic process shaped by continual gene gain and loss across species and strains. This genomic flexibility allows ...

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Education

Enseignement

JoVE Core

Microbiology

Microbiologie

Unit

Unité

Microbial Evolution

Évolution microbienne

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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 with the strains studied.

The pan-genome includes every gene found across all strains of a species. It contains both the core genes and genes found only in certain strains. In Salmonella enterica, strains such as S. enterica Typhimurium add unique genes that expand the pan-genome.

Horizontal gene transfer, or HGT, is a major way microbes gain new genes. It can give them traits that help them resist antibiotics, use new nutrients, or live in new habitats. Some acquired genes are not useful and may later be removed by genome deletions or genetic drift, which helps keep many microbial genomes streamlined. In some niches, however, microbes expand their gene sets when they need wider metabolic abilities.

Comparative genomics has also shown that bacterial and archaeal genomes share a small group of about 30 to 60 gene families. These conserved genes carry out DNA replication, transcription, translation, and core metabolism. Together, gene acquisition, gene loss, and selective retention show how microbial genomes stay flexible while still keeping essential biological functions.

Microbial Core and Pan-Genome Changes

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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 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

Learn how microbial genomes change through gene gain, gene loss, HGT, core genes, and pan-genomes using Salmonella enterica as an example.

Microbial Core and Pan-Genome Changes | 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

Microbial Core and Pan-Genome Changes

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