Chemoautotrophs: Where They Live and What They Eat

Anne Kamiya, Adrianne Baron
  • Author
    Anne Kamiya

    Anne has experience in science research and writing. She has a graduate degree in nutrition (gut microbiome & nutritional microbiology) and undergraduate degrees in microbiology (immunology & medical microbiology) and English (myth & folklore). She has also worked as an ocean & Earth science educator.

  • Instructor
    Adrianne Baron

    Adrianne has a master's degree in cancer biology and has taught high school and college biology.

Explore chemoautotrophs. Learn the definition of a chemoautotroph and understand its energy sources. Discover examples of chemoautotrophs and find where they live. Updated: 02/28/2022

Table of Contents


What are Chemoautotrophs?

When energy is produced, not from eating food or nutrients, but from oxidizing inorganic chemicals, that organism is called a chemoautotroph. The chemoautotroph definition breaks down as follows: chemo means "relating to chemicals," auto means "self," and troph means "food." So, a chemoautotroph literally means something that creates its own food from chemicals.

Within an ecosystem, chemoautotrophs are vital because they are often the main, or primary producers, of food for everything else within that ecosystem. A good example of primary producers are plants. Plants are photoautotrophs. This term means they are able to create their own food from sunlight. Through photosynthesis, plants transform light energy into organic compounds like leaves, roots, fruit, and seeds for animals to eat. The herbivores that survive off of plants are called primary consumers. Even predators like lions eat the primary consumers that live off of plants to survive. Without primary producers, there is nothing for the primary consumers to eat and the entire ecosystem falls apart. The situation with chemoautotrophs is similar. They are the main producers that turn inorganic chemicals into organic compounds. Without them, the entire ecosystem would collapse.

Plants are the primary producers of terrestrial (land) food webs but also depend on nitrogen-fixing bacteria. In the deep ocean where there is no light to photosynthesize, chemoautotrophs turn inorganic chemicals into energy and become the primary producers of deep ocean food webs

Food webs for the land and ocean.

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  • 0:01 What Is a Chemoautotroph?
  • 0:35 Groups of Chemoautotrophs
  • 1:12 Examples of Chemoautotrophs
  • 2:40 Lesson Summary
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Where are Chemoautotrophs Found?

Chemoautotrophs are microorganisms that turn inorganic chemicals into energy and use that energy to reproduce, grow and survive. Chemoautotrophic bacteria and archaea can live in places where there is little or no sunlight. They may also live in areas rich in inorganic chemicals. Some examples of places where chemoautotrophs live is in the soil, deep ocean, geysers, hot springs, or iron-rich rivers and wells.

But how do chemoautotrophs make their own energy from inorganic chemicals? They do it through a process called chemolithotrophy, where inorganic chemicals are oxidized to provide energy in the form of electrons. Oxidation is a process where electrons are taken away, or lost, from a molecule or atom. Oxidation frequently involves oxygen, but oxygen is not required for an oxidation reaction to occur. The inorganic chemicals that give chemoautotrophs their energy in the form of electrons are electron donors.

Chemoautotroph energy sources can come from organic or inorganic chemicals, depending on the organism. Chemoautotrophs that obtain energy from oxidizing inorganic chemicals are also sometimes called chemolithoautotrophs. However, when a chemoautotroph produces energy from oxidizing organic chemicals, that organism is instead called a chemoorganoautotroph.

Chemoautotroph Energy Sources

Some examples of chemoautotroph energy sources from inorganic chemicals include nitrogen, sulfur, and iron. Chemoorganoautotrophs, on the other hand, obtain energy from a variety of organic compounds and get their carbon from carbon dioxide.

Chemoautotrophs Examples

Three major types of chemoautotrophic microorganisms are sulfur-oxidizing chemotrophs, nitrogen-fixing bacteria, and iron-oxidizing bacteria. They will be discussed in detail in the next three sections.

Sulfur-Oxidizing Chemotrophs

Photosynthetic organisms like algae are primary producers for the upper ocean. However, photosynthetic life cannot survive where sunlight cannot reach, beyond the epipelagic and mesopelagic zones starting at 300 meters below the surface of the ocean. Deep sea volcanic vents, called hydrothermal vents, are scattered throughout the bottom of the ocean with temperatures as high as 380 degrees Celsius. They also spew out hydrogen sulfide, an inorganic chemical pulled from the deep earth. In these ecosystems, sulfur-oxidizing archaea and bacteria oxidize inorganic elemental sulfur or hydrogen sulfide, turning sulfur into organic sulfate during the process. These bacteria are then eaten by other small marine organisms (primary consumers) like tube worms and shrimp. Chemoautotrophs are the primary producers of the deep sea and form the framework for this ecosystem.

The upper portion of the ocean near the surface where sunlight permeates is called the epipelagic and mesopelagic zone. Starting at about 300 meters deep, sunlight starts to become completely nonexistent in the deeper abyss.

A cartoon of the ocean showing the different zones based on depth.

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Frequently Asked Questions

What bacteria are chemoautotrophic?

Nitrogen-fixing bacteria and iron-oxidizing bacteria are chemoautotrophic. Nitrogen-fixing soil bacteria are important for the nitrogen cycle. Nitrogen fixing bacteria in oceans, lakes or brackish water are called cyanobacteria. Although they are important to these ecosystems, an excess of cyanobacteria cause algal blooms, which can be toxic. Iron-oxidizing bacteria subsist in areas rich in iron, including plumbing pipes and water storage tanks. They can be a nuisance because of the slime and organic chemicals they produce.

What are chemoautotrophic organisms?

Chemoautotrophic organisms are able to produce their own energy from organic or inorganic compounds. When the energy source is from an organic compound, the chemoautotroph is called a chemoorganoautotroph. When the energy source is from an inorganic compound, the chemoautotroph is called a chemolithoautotroph. Chemoautotroph is a broad category that includes both of these groups.

How does a chemoautotroph get energy?

Chemoautotrophs get energy from inorganic chemicals. They do this by a process called oxidation, which allows the chemoautotroph to extract the energy they need as electrons.

What are examples of chemoautotrophs?

Chemoautotrophs are microorganisms such as bacteria and archaea. Some examples are sulfur-oxidizing archaea and bacteria, nitrogen-fixing bacteria, and iron-oxidizing bacteria.

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