What Are Autotrophs: Types and Examples

By: Tom Frankel
Post Date: June 29th 2023

Types of Autotrophs

People familiar with autotrophs know just how crucial they are in the food chain. As food chain producers, autotrophs create their own energy and nutrients through photosynthesis and chemosynthesis. Unlike animals and humans, they have the unique ability to produce their own food from components in their environment.

What is autotrophic and its types? Learn more about these organisms, how they make food and some examples of autotrophs.

What Is Meant by Autotrophs?

Autotrophs, or primary producers, are organisms that can produce their own food from natural sources like water, light energy, carbon dioxide (CO₂) and chemical energy. They can feed themselves without assistance from other organisms. The term comes from “auto,” meaning “self,” and “troph,” meaning “food.”

Other life forms can’t exist without autotrophs, making them essential. Without plants that produce sugars through photosynthesis, herbivorous animals couldn’t exist. That means carnivorous animals that depend on herbivores wouldn’t exist, either.

Autotrophs are the foundation of the ecosystem energy pyramid. They provide the food that heterotrophs — organisms that can’t produce their own food — need to live.

How Many Types of Autotrophic Nutrition Are There?

There are two types of autotrophic nutrition — photosynthesis and chemosynthesis. Photosynthesis uses sunlight, while chemosynthesis uses chemical energy. Here are the primary differences between them:

• Photosynthesis: Photosynthesis uses CO₂, solar energy and water to generate oxygen and energy in the form of sugar. It occurs in plants and certain bacteria wherever adequate sunlight is present — this could be on land, in shallow water or even in or below clear ice. All photosynthetic organisms use sunlight to turn CO₂ and water into sugar.
• Chemosynthesis: Occurring in bacteria and other organisms, chemosynthesis uses energy from inorganic chemical reactions to make sugar. All chemosynthetic organisms use energy from chemical reactions to produce food, though this process can look slightly different depending on the species.

What Are Examples of Autotrophs?

There are several forms of photosynthetic and chemosynthetic autotrophs. Here are some different types of bacteria and plants that can produce their own food.

1. Algae

Green algae, which many know as pond scum, is a type of photosynthetic autotroph. Algae are found in water worldwide, including freshwater, saltwater and brackish water. They contain chlorophyll, a green-colored pigment that absorbs energy from the sun and allows them to photosynthesize. Larger forms of algae are known as seaweed.

2. Iron Bacteria

Many people have iron bacteria in their homes without realizing it. Iron bacteria create a rusty color in well water pipe linings and toilet tanks. They oxidize iron to produce food. This chemosynthetic autotroph is also present in iron-rich environments like hydrothermal vents and hot lava beds. Some types of iron-oxidizing bacteria include the following:

• Acidithiobacillus ferrooxidans
• Geobacter metallireducens
• Thiobacillus ferrooxidans
• Zetaproteobacteria

Iron bacteria oxidize ferrous ions to ferric ions. They convert iron atoms from a molecular form where they can’t dissolve in water to one where they can.

3. Sulfur Bacteria

Not all photosynthetic autotrophs are plants. As the name suggests, sulfur bacteria is a photoautotroph that converts sulfur into food. It’s often found in hot springs in mixed populations with cyanobacteria. It can also be found on the ocean floor or in well water. Sulfur bacteria thrive in sulfide-rich, dimly light environments.

There are two main types — green sulfur bacteria (GSB) and purple sulfur bacteria (PSB). While GSB appears a brown, yellow-green or green-orange color, PSB appears a purple or reddish-brown color. Both use various combinations of elemental sulfur, thiosulfate, sulfide and sometimes ferrous iron and hydrogen.

4. Cyanobacteria

Cyanobacteria is a photosynthetic autotroph believed to be Earth’s first oxygen producer. Also called blue-green algae or pond slime, cyanobacteria are present in nearly all types of water, including freshwater, saltwater and brackish water. It is the only bacteria capable of producing oxygen during photosynthesis.

They come in multiple forms, including the following:

• Nostoc
• Anabaena
• Microcystis
• Gloeocapsa
• Arthrospira platensis

5. Grass

Grass is another example of a photoautotroph, as it uses sunlight to create sugars. For instance, wild grasses commonly grow in the Rocky Mountains. Herbivores such as mule deer feed on the grasses. Then, carnivores like mountain lions consume the deer. There are many types of autotrophic grasses, including:

• Lawn grass
• Lemongrass
• Napier grass
• Pampas grass

6. Maize Plant

Grown in every continent except Antarctica, the maize plant — or corn — is a photosynthetic autotroph that uses C4 photosynthesis.

During C4 photosynthesis, which produces a four-carbon compound, CO₂ concentrates in “bundle sheath” cells around Rubisco, an enzyme in plant chloroplasts. This process delivers CO₂ directly to Rubisco, eliminating its contact with oxygen and the need for photorespiration. Like many C4 plants, maize has a particularly high photosynthesis rate and water efficiency.

7. Wheat

Wheat, one of the oldest cereal crops, is another photosynthetic autotroph that converts solar energy into glucose. There are multiple wheat varieties, including:

• Spelt
• Durum
• Einkorn
• Wild emmer
• Polish wheat
• Winter wheat
• Common wheat
• Triticum compactum

8. Phytoplankton

Phytoplankton are tiny, photoautotrophic organisms that live in the ocean and use light to produce food. Since they are weak swimmers, they’re usually found drifting in large bodies of water.

Phytoplankton are a primary food source for many aquatic animals, similar to plants on dry land. Different phytoplankton species include diatom, coccolithophore and bacterioplankton. Cyanobacteria and algae are also types of phytoplankton.

While all phytoplankton photosynthesize, some species consume other organisms for additional energy.

9. Hydrogen Bacteria

Hydrogen-oxidizing bacteria are chemoautotrophs that use hydrogen as an electron donor. They can be classified as aerobes or anaerobes:

• Aerobes: Aerobes use hydrogen as an electron donor and oxygen as an acceptor. Aerobic means “with air.”
• Anaerobes: Anaerobes also use hydrogen as an electron donor, but they use nitrogen or sulfate dioxide as electron acceptors. Anaerobic means “without air.”

Choose SSI for All Your Wastewater Needs

Various types of autotrophic bacteria — including iron, sulfur and hydrogen — are present in industrial wastewater. It’s important to remove bacteria and other potential contaminants through multi-step wastewater treatment. Having the proper equipment for this process is essential, as well.

SSI Aeration, Inc. specializes in wastewater and sewage treatment products for facilities in numerous industries. Plants can find nearly everything they need for wastewater treatment, including various diffusers and membranes to assist aeration. From textile manufacturers and food and beverage processors to alcoholic beverage producers and mining operations, SSI Aeration helps plants of all types find quality wastewater treatment equipment for their unique requirements.

As a global leader in water treatment equipment with a fully staffed engineering team, SSI is a trusted source for innovative water treatment solutions. Reach out to SSI today to learn more about available products and equipment.

Tom Frankel

Mr. Frankel co-founded SSI in 1995 with experience in design and distribution of engineered systems. He is in charge of sales, marketing and operations in the company. Mr. Frankel holds multiple US patents related to diffusers. He is a graduate of Washington University in St. Louis.