Name: microbial adaptation in changing environments
Uploaded: 2026-03-12T13:57:34.000Z
Duration: 1 min 24 s
Channel: JoVE

Os micróbios evoluem rapidamente devido aos tempos de geração curtos e grandes populações, tornando-os ideais para estudar a evolução em laboratório.A seleção natural atua sobre as variantes aleladas existentes na população, tornando os grupos com variantes úteis mais abundantes em ambientes mutáveis.Por exemplo, em condições anaeróbicas, Rhodobacter usa a luz para realizar a fotossíntese, utilizando os pigmentos bacterioclorofila e carotenoides.Durante escuridão prolongada, os pigmentos de Rhodobacter têm pouco benefício, favorecendo mutantes sem pigmento na população. Mas o tipo selvagem domina quando a luz retorna.Outro exemplo é o 'Experimento de Evolução a Longo Prazo' em andamento. Foi iniciada em 1988 com 12 populações idênticas de E. coli crescendo em um ambiente com glicose limitada.Desde então, esse experimento já acompanhou mais de 80.000 gerações.Com o tempo, uma população de E. coli adquiriu uma mutação rara. E permitiu que essa população metabolizasse citrato em condições ricas em oxigênio.Essa mutação proporcionou acesso a uma nova fonte de nutrientes e uma vantagem competitiva sobre seus ancestrais.

evolução de novos traços em microrganismos

Os microrganismos evoluem rapidamente devido ao seu grande tamanho populacional e curtos tempos de geração, frequentemente apresentando mudanças mensuráveis em poucos dias sob condições laboratoriais. A seleção natural atua sobre a variação genética permanente, permitindo a retenção e amplificação de traços benéficos que conferem vantagens de aptidão em ambientes em mudança.<h3>Regulação Adaptativa do Pigmento em Rhodobacter</h3>Em Rhodobacter, um gênero de bactérias roxas não sulfurosas, pigmentos que captam a luz como bacterioclorofila e carotenoides possibilitam a fotossíntese sob condições anaeróbias e iluminadas. A expressão desses pigmentos é rigidamente regulada pelos níveis de oxigênio e luz do ambiente para alinhar com a atividade fotossintética.No entanto, na escuridão, os pigmentos não oferecem benefício funcional e, em vez disso, impõem um fardo energético. Como resultado, mutantes que não possuem esses pigmentos surgem e são favorecidos em condições escuras devido à redução dos custos metabólicos. No entanto, quando a luz volta a estar disponível, esses mutantes deficientes em pigmento são superados por células selvagens capazes de fotossíntese.Esse padrão de seleção reversível apresenta um trade-off adaptativo, onde flutuações ambientais alteram o equilíbrio entre eficiência metabólica e aquisição de energia.<h3>Experimento de Evolução de Longo Prazo em E. coli</h3>Outro exemplo marcante da evolução microbiana é o Experimento de Evolução a Longo Prazo (LTEE), iniciado por Richard Lenski em 1988. Este estudo em andamento acompanhou populações de Escherichia coli cultivadas em meio com glicose limitada por mais de 80.000 gerações. Com o tempo, essas linhagens evoluíram para várias adaptações, incluindo aumento do tamanho celular, taxas de crescimento mais rápidas e vias metabólicas otimizadas.<h3>Evolução da Utilização do Citrato</h3>Mais notavelmente, uma linhagem evoluiu a capacidade de metabolizar citrato em condições aeróbias — uma característica tipicamente ausente em E. coli selvagem, que não pode importar citrato na presença de oxigênio. Essa inovação permitiu que a cepa mutante explorasse um recurso que de outra forma seria inacessível, ganhando uma vantagem seletiva significativa.Análises genéticas revelaram que essa característica surgiu por meio de uma série de mutações — inicialmente estabelecendo o potencial para utilização de citrato (potenciação), seguida por mutações que permitiam sua expressão e transporte reais (atualização). Essa descoberta destaca a interação entre contingência, mutação e seleção natural na inovação evolutiva.Juntos, esses estudos exemplificam como sistemas microbianos servem como modelos dinâmicos para observar processos evolutivos em tempo real. Eles apresentam tanto forças determinísticas quanto eventos estocásticos que impulsionam a diversidade biológica e a inovação.

Evolução de Novos Traços em Microrganismos

Microorganisms evolve rapidly due to their large population sizes and short generation times, often exhibiting measurable changes within days under ...

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Education

JoVE Core

Microbiology

Microbiologia

Unit

Unidade

Microbial Evolution

Evolução Microbiana

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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 without waiting for brand-new mutations.

One example is Rhodobacter, a group of purple non-sulfur bacteria. These cells use light-harvesting pigments such as bacteriochlorophyll and carotenoids to support photosynthesis when oxygen is low and light is available. Their pigment production is tightly controlled by oxygen and light levels.

In darkness, those pigments no longer help the cells. They also cost energy to make and maintain. Because of that cost, mutants that lose the pigments can be favored in the dark. When light returns, wild-type cells that can photosynthesize again outcompete the pigment-deficient mutants. This is a reversible selection pattern that shows a trade-off between saving energy and capturing light.

A second major example is the Long-Term Evolution Experiment, or LTEE, started by Richard Lenski in 1988. The study has followed Escherichia coli grown in a glucose-limited medium for more than 80,000 generations. Over time, these lineages evolved changes such as larger cell size, faster growth, and better metabolic pathways.

The best-known LTEE result is one lineage that gained the ability to use citrate under aerobic conditions. Wild-type E. coli usually cannot import citrate when oxygen is present, so this trait opened access to a new food source. Genetic analysis showed that the trait appeared through a series of mutations. First came potentiation, which created the potential for citrate use. Then later mutations enabled actualization, or the real expression and transport of citrate.

Together, these microbial studies show evolution in real time. They highlight how mutation, natural selection, chance, and environmental change can work together to create new traits and shape biological diversity.

Microbial Adaptation in Changing Environments

microbial-adaptation-in-changing-environments

origin of cellular life

How Early Cells Got Their Start

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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 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

See how microbes adapt through natural selection, pigment changes in Rhodobacter, and the E. coli LTEE, including the evolution of citrate use.

Microbial Adaptation in Changing Environments | 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 Adaptation in Changing Environments

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