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

由于微生物具有较短的世代时间和庞大的种群规模，进化速度很快，因此非常适合在实验室中用于研究进化过程。自然选择作用于种群中已有的等位基因变异，使具有有利变异的群体在变化的环境中更加丰富。例如，在厌氧条件下，Rhodobacter 利用光能进行光合作用，所用色素包括细菌叶绿素和类胡萝卜素。在长时间黑暗条件下， 红细菌属 色素几乎没有优势，有利于种群中缺乏色素的突变体。但当光照恢复时，野生型重新占据主导地位。另一个例子是正在进行的“长期进化实验”。该实验始于1988年，最初使用12个相同的大肠杆菌（E. coli）种群，在葡萄糖受限的环境中进行培养。自那以来，该实验已追踪了超过 80,000 代。随着时间的推移，一个E. coli种群获得了一种罕见的突变，使该种群能够在富氧条件下代谢柠檬酸盐。这种突变使生物获得了新的营养来源，并相对于其祖先具有竞争优势。

微生物中新性状的演化

Evolution of New Traits in Microbes

由于微生物种群规模庞大且世代时间短，在实验室条件下通常在数天内即可观察到明显的进化变化。自然选择作用于已有的遗传变异，使得在变化的环境中具有适应性优势的有益性状得以保留和扩增。<h3>适应性色素调控在 Rhodobacter</h3>在红细菌属（Rhodobacter）——一种紫色非硫细菌——中，细菌叶绿素和类胡萝卜素等光捕获色素能够在无氧且光照条件下进行光合作用。这些色素的表达受到环境氧气和光照水平的严格调控，以与光合作用活性相协调。然而，在无光条件下，这些色素无法提供任何功能优势，反而会带来能量负担。因此，缺乏这些色素的突变体得以产生，并因代谢成本降低而在黑暗环境中受到选择优势。然而，当光照再次出现时，这些色素缺陷型突变体便会被具备光合作用能力的野生型细胞所淘汰。这种可逆选择模式表现出一种适应性权衡，即环境波动改变了代谢效率与能量获取之间的平衡。<h3>长期进化实验 E. coli</h3>微生物进化的另一个标志性实例是理查德·伦斯基（Richard Lenski）于1988年启动的长期进化实验（Long-Term Evolution Experiment, LTEE）。该持续进行的研究已追踪在葡萄糖限制培养基中培养的Escherichia coli种群超过80,000代。随着时间推移，这些菌系进化出多种适应性特征，包括细胞体积增大、生长速率加快以及代谢通路的优化。<h3>柠檬酸盐利用的进化</h3>最显著的是，其中一个菌系进化出了在有氧条件下代谢柠檬酸盐的能力——这一特性在野生型 E. coli 中通常不存在，因为野生型在有氧条件下无法摄取柠檬酸盐。这一创新使突变菌株能够利用原本无法获取的资源，从而获得显著的选择优势。基因分析表明，该性状的产生经历了一系列突变——最初是获得了利用柠檬酸盐的潜力（致敏化），随后是使该潜力得以实际表达和转运的突变（实现化）。这一发现凸显了偶然性、突变与自然选择在进化创新中的相互作用。这些研究共同展示了微生物系统如何作为动态模型，用于实时观察进化过程，揭示了推动生物多样性和创新的确定性因素与随机事件。

微生物由于种群数量庞大且世代时间短，进化速度很快，通常在几天内就会在……下表现出可测量的变化

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Education

教育

JoVE Core

Microbiology

微生物学

Unit

单元

Microbial Evolution

微生物进化

KEY TERMS AND CONCEPTS

关键术语与概念

微生物新性状的进化

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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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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