Name: reading microbial family trees
Uploaded: 2026-03-12T13:57:34.000Z
Duration: 1 min 28 s
Channel: JoVE

Un árbol filogenético representa relaciones evolutivas entre microorganismos y a menudo depende de secuencias de ADN, ARN o proteínas.En los filogramas, las especies aparecen en las puntas, y la longitud de las ramas refleja la cantidad de cambio de secuencia.Los árboles enraizados marcan ancestros comunes y puntos de divergencia, mientras que los árboles sin raíces muestran vínculos sin dirección evolutiva.Los árboles filogenéticos utilizan secuencias homólogas, especialmente ortólogos, que son genes homólogos separados por especiación.Los genes de subunidad rRNA pequeña altamente conservados, como el gen 16S rRNA, actúan como marcadores universales para comparaciones microbianas.El ADN de estos genes marcadores en las muestras se secuencia.Las secuencias se alinean para identificar desajustes y huecos derivados de inserciones o eliminaciones.Luego, la distancia evolutiva se mide como la relación entre las diferencias de nucleótidos y el número total de posiciones alineadas.Los árboles filogenéticos a veces pueden ser engañosos cuando rasgos similares evolucionan de forma independiente o cuando la transferencia horizontal de genes introduce genes a través de linajes no relacionados, produciendo historias génicas que no reflejan la historia evolutiva real de los organismos.

filogenia microbiana

Comprender las relaciones evolutivas entre microorganismos es fundamental para la ecología microbiana y la taxonomía. Los árboles filogenéticos son herramientas esenciales para inferir estas relaciones, basándose principalmente en análisis comparativos de secuencias moleculares como el ADN, el ARN o las proteínas. En estudios microbianos, estos árboles suelen representar las trayectorias evolutivas de diversas especies bacterianas y arqueales al mapear las diferencias genéticas acumuladas a lo largo del tiempo.Los árboles filogenéticos están compuestos por puntas, ramas y nudos. Las puntas representan especies existentes o muestreadas, mientras que las ramas trazan trayectorias evolutivas. Las longitudes de las ramas son proporcionales al número de cambios genéticos inferidos entre los nodos. Los árboles enraizados resaltan un ancestro común y divergencia direccional, mientras que los árboles sin raíces simplemente muestran la relación sin asumir un punto de origen. Los nodos internos representan formas ancestrales hipotéticas y pueden marcar eventos de especiación o divergencia.En filogenética microbiana, los genes altamente conservados —particularmente el ARN ribosómico de subunidad pequeña (ARNr de la SSU)— se utilizan comúnmente debido a su presencia en todos los dominios de la vida y a su lenta tasa evolutiva. Estos marcadores genéticos universales permiten comparaciones a lo largo de amplias distancias filogenéticas. Se seleccionan genes homólogos, y preferiblemente ortólogos, para la construcción en árbol para asegurar que las secuencias compartan una ascendencia y función comunes. Los ortólogos suelen identificarse mediante búsquedas recíprocas de mejor impacto (por ejemplo, BLAST) o canalizaciones ortológicas, y luego se amplifican mediante cebadores específicos del locus (o enriquecimiento dirigido) entre taxones. Los amplicones o fragmentos enriquecidos resultantes se secuencian (a menudo usando plataformas de alto rendimiento) y se filtran por calidad. Estas secuencias se alinean para detectar sustituciones, inserciones o deleciones en posiciones homólogas. Las distancias evolutivas se cuantifican por el grado de divergencia de secuencia.Aunque los árboles filogenéticos ofrecen conocimientos clave, no siempre reflejan historias evolutivas reales. Las transferencias genéticas horizontales pueden dar lugar a similitudes engañosas. Para abordar esto, métodos como la parsimonia máxima evalúan alineamientos de secuencias para inferir árboles que requieren menos cambios evolutivos. Otros enfoques, como la máxima verosimilitud y la inferencia bayesiana, también se utilizan comúnmente para la construcción de árboles y a menudo proporcionan modelos estadísticamente más robustos de la evolución.

Filogenia microbiana

Understanding the evolutionary relationships among microorganisms is fundamental to microbial ecology and taxonomy. Phylogenetic trees are essential tools ...

https://cloudfront.jove.com/files/ftp_upload/40724/40724_article_thumb_40724.jpg

Education

Educación

JoVE Core

Microbiology

Microbiología

Unit

Unidad

Microbial Evolution

Evolución microbiana

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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. Rooted trees show a common ancestor and a direction of divergence, while unrooted trees show relatedness without naming an origin point. Internal nodes stand for hypothetical ancestors and can represent speciation or other divergence events.

Microbial phylogenetics often relies on highly conserved genes. Small subunit ribosomal RNA, or SSU rRNA, is a common marker because it is found across all domains of life and changes slowly. These universal markers make it possible to compare organisms that are very far apart on the evolutionary tree. Researchers choose homologous genes, and preferably orthologous genes, so the sequences share common ancestry and function.

To build a tree, scientists first identify orthologs with reciprocal best-hit searches such as BLAST or with orthology pipelines. They then use locus-specific primers or targeted enrichment to amplify the genes across taxa. The resulting amplicons or enriched fragments are sequenced, often with high-throughput platforms, and quality-filtered before analysis.

Next, the sequences are aligned so scientists can spot substitutions, insertions, and deletions at matching positions. Evolutionary distance is estimated from how much the sequences differ. Even so, a tree may not always show the true history of a group, because horizontal gene transfer can create misleading similarities. To reduce that problem, scientists may use maximum parsimony, which chooses the tree with the fewest changes. Maximum likelihood and Bayesian inference are also common methods, and they often give more statistically robust models of evolution.

Reading Microbial Family Trees

origin of cellular life

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...

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 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 phylogenetic trees use DNA, RNA, and protein sequences to show relationships among bacteria and archaea, and how scientists build them.

Reading Microbial Family Trees | 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

Reading Microbial Family Trees

Description

Transcript

Tags