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

I microbi evolvono rapidamente a causa dei tempi di generazione brevi e delle grandi dimensioni delle popolazioni, rendendoli ideali per studiare l'evoluzione in laboratorio.La selezione naturale agisce sulle varianti alleli esistenti nella popolazione, rendendo i gruppi con varianti utili più abbondanti in ambienti mutevoli.Ad esempio, in condizioni anaerobiche, Rhodobacter utilizza la luce per effettuare la fotosintesi, utilizzando i pigmenti batterioclorofilla e carotenoidi.Durante l'oscurità prolungata, i pigmenti di Rhodobacter hanno scarsi benefici, favorendo i mutanti privi di pigmento nella popolazione. Ma il tipo selvatico domina quando la luce ritorna.Un altro esempio è l'esperimento in corso chiamato 'Long-Term Evolution Experiment'. È stato avviato nel 1988 con 12 popolazioni identiche di E. coli che crescevano in un ambiente a basso contenuto di glucosio.Da allora, questo esperimento ha tracciato più di 80.000 generazioni.Col tempo, una popolazione di E. coli ha acquisito una rara mutazione. E ha permesso a questa popolazione di metabolizzare il citrato in condizioni ricche di ossigeno.Questa mutazione ha fornito accesso a una nuova fonte di nutrienti e un vantaggio competitivo rispetto ai loro antenati.

evoluzione di nuovi tratti nei microbi

Evolution of New Traits in Microbes

I microrganismi si evolvono rapidamente a causa delle grandi dimensioni delle popolazioni e dei tempi di generazione brevi, spesso mostrando cambiamenti misurabili nel giro di pochi giorni in condizioni di laboratorio. La selezione naturale agisce sulla variazione genetica permanente, permettendo la conservazione e l'amplificazione di tratti benefici che conferiscono vantaggi di fitness in ambienti mutevoli.<h3>Regolazione adattiva del pigmento in Rhodobacter</h3>In Rhodobacter, un genere di batteri viola non zolfosi, pigmenti che assorbono la luce come batterioclorofilla e carotenoidi permettono la fotosintesi in condizioni anaerobiche e illuminate. L'espressione di questi pigmenti è strettamente regolata dai livelli ambientali di ossigeno e luce per allinearsi all'attività fotosintetica.Tuttavia, nell'oscurità, i pigmenti non offrono alcun beneficio funzionale e impongono invece un peso energetico. Di conseguenza, i mutanti privi di questi pigmenti nascono e sono preferiti in condizioni oscure grazie ai ridotti costi metabolici. Tuttavia, quando la luce torna disponibile, questi mutanti carenti di pigmento vengono superati da cellule di tipo selvatico capaci di fotosintesi.Questo schema di selezione reversibile mostra un compromesso adattivo, in cui le fluttuazioni ambientali spostano l'equilibrio tra efficienza metabolica e acquisizione di energia.<h3>Esperimento evolutivo a lungo termine in E. coli</h3>Un altro esempio emblematico di evoluzione microbica è il Long-Term Evolution Experiment (LTEE), avviato da Richard Lenski nel 1988. Questo studio in corso ha monitorato popolazioni di Escherichia coli coltivate in un mezzo a glucosio limitato per oltre 80.000 generazioni. Nel tempo, queste linee hanno evoluto varie adattazioni, tra cui aumento della dimensione cellulare, tassi di crescita più rapidi e vie metaboliche ottimizzate.<h3>Evoluzione dell'utilizzo del citrato</h3>In particolare, una linea ha evoluto la capacità di metabolizzare il citrato in condizioni aerobiche—un tratto tipicamente assente nell'E. coli di tipo selvatico, che non può importare citrato in presenza di ossigeno. Questa innovazione permise alla variante mutante di sfruttare una risorsa altrimenti inaccessibile, ottenendo un significativo vantaggio selettivo.Le analisi genetiche hanno rivelato che questo tratto derivava da una serie di mutazioni—inizialmente stabilendo il potenziale per l'utilizzo del citrato (potenziazione), seguito da mutazioni che ne consentivano la reale espressione e il trasporto (attualizzazione). Questa scoperta evidenzia l'interazione tra contingenza, mutazione e selezione naturale nell'innovazione evolutiva.Insieme, questi studi esemplificano come i sistemi microbici fungano da modelli dinamici per osservare i processi evolutivi in tempo reale. Mostrano sia forze deterministiche sia eventi stocastici che guidano la diversità biologica e l'innovazione.

Evoluzione di nuovi tratti nei microbi

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

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JoVE Core

Microbiology

Microbiologia

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Microbial Evolution

Evoluzione microbica

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

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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...

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How DNA Defines Microbial Species

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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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