Difference Between Phototrophs and Chemotrophs

Main Difference – Phototrophs vs Chemotrophs

Phototrophs and chemotrophs are two types of nutritional groups found in the environment. Most phototrophs are autotrophs, using the energy from sunlight to produce their food. Chemotrophs oxidize inorganic compounds or organic compounds as their energy source. They are the primary producers of food chains. The main difference between phototrophs and chemotrophs is that phototrophs capture protons in order to acquire energy whereas chemotrophs oxidize electron donors in order to acquire energy.

This article explains,

1. What are Phototrophs
      – Definition, Characteristics, Classification
2. What are Chemotrophs
      – Definition, Characteristics, Classification
3. What is the difference between Phototrophs and Chemotrophs

Difference Between Phototrophs and Chemotrophs - Comparison Summary

What are Phototrophs

The organisms which perform proton capturing in order to acquire energy are known as phototrophs. Hence, phototrophs utilize the energy from light to produce food in the form of organic compounds. These complex organic compounds are ultimately used to energize cellular metabolic processes. Photosynthesis is the major process of capturing protons. During photosynthesis, carbon dioxide is anabolically converted into organic material. These organic materials are also used to build structures. Glucose is the primary form of the organic compound produced in the photosynthesis. It is polymerized to form carbohydrates, starch, proteins and fats as complex organic compounds.

Phototrophs use either electron transport chain or direct proton pumping to generate the electro-chemical gradient used in the ATP synthase. ATP provides the chemical energy for cellular functions.

Classification of Phototrophs

Phototropes are either autotrophs or heterotrops. Photoautotrophs fix carbon into simple sugars using light as the energy source. Examples for photoautotrophs are green plants, algae and cyanobacteria. Holotrophs are carbon fixing organisms from carbon dioxide. Phototrophs which use chlorophyll in order to capture the light energy, splitting water to produceoxygon are oxygenicphotosynetic organisms.

Difference Between Phototrophs and Chemotrophs

Figure 1: Terrestrial and Aquatic Photoautotrophs

Photoheterotrophs use energy from light, and their carbon source is organic compounds. Examples for photoheterotrophs are some bacteria like Rhodobactor.

What are Chemotrophs

The organisms which obtain their energy by oxidizing electron donors are known as chemotrophs. Their carbon source can be either inorganic carbon or organic carbon. Chemosynthesis is the primary production metabolism in chemotrophs. During chemosynthesis, simple carbon containing molecules like carbon dioxide or methane is used to produce organic compounds as nutrients by oxidizing hydrogen gas or hydrogen sulfide. Chemotrophs consist of biogeochemically important taxa like sulfur oxidizing proteobacteria, aquificaeles, neutrophilic iron-oxidizing bacteria and methanogenic archaea.

Organisms that exit in the dark like oceans use chemosynthesis in order to produce their food. When hydrogen gas is available, the reaction between carbon dioxide and hydrogen produces methane. In the oceans, ammonia and hydrogen sulfide are oxidized to produce their food with or without oxygen. Chemosynthetic bacteria are consumed by organisms in the ocean in order to carry out symbiotic relationship. Secondary producers in hydrothermal vents, cold seeps, methane clathrates and isolated cave water are benefited by chemotrophs. 

Classification of Chemotrophs

Two types of chemotrophs can be identified: chemoorganotrophs which oxidize organic compounds for energy, and chemolithotrophs, which oxidize inorganic compounds for energy. Chemolithotrophs use electrons from inorganic chemical sources like hydrogen sulfide, ammonium ions, ferrous ions and elemental sulfur. Examples for chemolithotrophs include Acidithiobacillus ferrooxidans, Nitrosomonas, Nitrobactor and Algae.

Chemotrophs also can be either autotrophs or heterotrophs. Chemoautotrophs can be identified in ocean floors like underwater volcanos, independent from sunlight. Chemosynthetic bacteria replace the guts of giant tube worms like Riftia pachyptila in the ocean.  

Main Difference -  Phototrophs vs  Chemotrophs

Figure 2: Riftia pachyptila

Difference Between Phototrophs and Chemotrophs


Phototrophs: The organisms which capture proton  in order to acquire energy are known as phototrophs.

Chemotrophs: The organisms which obtain their energy by oxidizing electron donors are known as chemotrophs.

Energy Source

Phototrophs: The energy source of phototrophs is mainly sunlight.

Chemotrophs: The energy source of the chemotrophs is the oxidizing energy of chemical compounds.


Phototrophs: Phototropes are either photoautotrophs or photoheterotrophs.

Chemotrophs: Chemotrophs are either chemoorganotrophs or chemolithotrophs.


Phototrophs: Plants, algae, cyanobacteria are photoautotrophs, and purple non-sulfur bacteria, green non-sulfur bacteria, and heliobacteria are photoheterotrophs

Chemotrophs: Most bacteria like Acidithiobacillus ferrooxidans, Nitrosomonas, Nitrobacter and Algae are chemolithotrophs.


Both phototrophs and chemotrophs are two nutritional groups found in the environment. Both of them are found in autotrophic and heterotrophic forms. Thus, their autotrophs produce their own food while their heterotrophs consume other organisms’ food. They can be also found in primary and secondary levels of the food chain. The main difference between phototrophs and chemotrophs is their energy source.

1.”Phototroph”. En.wikipedia.org. N.p., 2017. Web. 8 Mar. 2017.
2.”Chemotroph”. En.wikipedia.org. N.p., 2017. Web. 8 Mar. 2017.
3.”Chemosynthesis”. En.wikipedia.org. N.p., 2017. Web. 8 Mar. 2017.

Image Courtesy:
1. “Dead tree river” (CC BY-SA 3.0) via Commons Wikimedia
2. “Gollner Riftia pachyptila” By Sabine Gollner et al. – Sabine Gollner, Barbara Riemer, Pedro Martínez Arbizu, Nadine Le Bris, Monika Bright (2011): Diversity of Meiofauna from the 9°50′N East Pacific Rise across a Gradient of Hydrothermal Fluid Emissions. PLoS ONE 5(8): e12321. doi:10.1371/journal.pone.0012321 (CC BY 2.5) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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