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

Microbes evolve rapidly because of short generation times and large population sizes, making them ideal for studying evolution in the lab.Natural selection acts on the existing allele variants in the population, making groups with helpful variants more abundant in shifting environments.For example, in anaerobic conditions, Rhodobacter uses light to perform photosynthesis, using the pigments bacteriochlorophyll and carotenoids.During prolonged darkness, Rhodobacter's pigments have little benefit, favoring pigment-lacking mutants in the population. But the wild type dominates once light returns.Another example is the ongoing &#8216;Long-Term Evolution Experiment.' It was started in 1988 with 12 identical populations of E. coli growing in a glucose-limited environment.Since then, this experiment has tracked more than 80,000 generations.Over time, one E. coli population gained a rare mutation. And it allowed this population to metabolize citrate in oxygen-rich conditions.This mutation provided access to a new nutrient source and a competitive advantage over their ancestors.

evolution of new traits in microbes

Microorganisms evolve rapidly due to their large population sizes and short generation times, often exhibiting measurable changes within days under laboratory conditions. Natural selection acts on standing genetic variation, enabling the retention and amplification of beneficial traits that confer fitness advantages in changing environments.<h3>Adaptive Pigment Regulation in Rhodobacter</h3>In Rhodobacter, a genus of purple non-sulfur bacteria, light-harvesting pigments such as bacteriochlorophyll and carotenoids enable photosynthesis under anaerobic, illuminated conditions. The expression of these pigments is tightly regulated by environmental oxygen and light levels to align with photosynthetic activity.However, in darkness, the pigments offer no functional benefit and instead impose an energetic burden. As a result, mutants that lack these pigments arise and are favored under dark conditions due to reduced metabolic costs. Nevertheless, when light becomes available again, these pigment-deficient mutants are outcompeted by wild-type cells capable of photosynthesis.This pattern of reversible selection shows an adaptive trade-off, where environmental fluctuations shift the balance between metabolic efficiency and energy acquisition.<h3>Long-Term Evolution Experiment in E. coli</h3>Another hallmark example of microbial evolution is the Long-Term Evolution Experiment (LTEE), initiated by Richard Lenski in 1988. This ongoing study has tracked Escherichia coli populations cultured in a glucose-limited medium for over 80,000 generations. Over time, these lineages have evolved various adaptations, including increased cell size, faster growth rates, and optimized metabolic pathways.<h3>Evolution of Citrate Utilization</h3>Most notably, one lineage evolved the ability to metabolize citrate under aerobic conditions&#8212;a trait typically absent in wild-type E. coli, which cannot import citrate in the presence of oxygen. This innovation enabled the mutant strain to exploit an otherwise inaccessible resource, gaining a significant selective advantage.Genetic analyses revealed that this trait arose through a series of mutations&#8212;initially establishing the potential for citrate utilization (potentiation), followed by mutations that enabled its actual expression and transport (actualization). This finding highlights the interplay of contingency, mutation, and natural selection in evolutionary innovation.Together, these studies exemplify how microbial systems serve as dynamic models for observing evolutionary processes in real time. They showcase both deterministic forces and stochastic events that drive biological diversity and innovation.

Evolution of New Traits in Microbes

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

Unit

Microbial Evolution

KEY TERMS AND CONCEPTS

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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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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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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