Lithotroph vs. Autotroph

The below article talks about what lithotrophs and autotrophs are, provides some examples, and includes other frequently asked questions about the same. 

What is the difference between lithotrophs and autotrophs?

Different organisms can be classified based on the energy source they use, where they source it from, how they have sourced it, etc. In laymen’s terms, an organism that can produce its own food using energy from light, water, carbon dioxide, etc. are autotrophs. A lithotroph is an organism that derives its energy from reduced inorganic substances such as hydrogen sulfide, carbon dioxide, etc. Lithotrophy is only experienced amongst microbes. 

Autotrophs 

An autotroph is an organism that is capable of producing its own energy for sustenance from its environment, such as by using light, water, carbon dioxide, etc. Since these organisms are capable of producing their own source of energy, they are also referred to ask producers. Some of the most common autotrophs we see around us include plants, algae, some bacteria, etc. All green plants utilize photosynthesis to gain energy and are thus categorized as autotrophs. Most autotrophs use photosynthesis through sunlight, water, and carbon dioxide to form energy. Some rare species of autotrophs would use chemosynthesis, rather than photosynthesis. Organisms that use this method, do not use sunlight to produce energy, rather they would use the energy released from different chemical reactions, the most common reaction being the combining of hydrogen sulfide and methane with oxygen, liberating energy that is absorbed by some autotrophs to perform chemosynthesis (Rutledge K. et.al., 2011). 

Source: Anonim O., 2020

An autotroph can feed itself without help from another organism, and are capable of creating organic substances from inorganic materials. Autotrophs form the lowest level of the food chain, since they are independent of other organisms for their survival. Autotrophs are important in the environment since they would be consumed as food for organisms that are higher up on the food chain. They play an important role in the environment around us. Think of it this way, if there are no plants or trees to convert sunlight, carbon dioxide, and water into energy through photosynthesis, there would not be herbivores (they sustain on plants and such matter), and without herbivores, there wouldn’t be carnivores. Essentially, without autotrophs, there is no animal kingdom. 

Source: Gorane J., 2021

Lithotrophs 

Organisms can be identified by the specific energy source they use. All energy is received or transmitted through the transfer of electrons, however, some organisms gain this energy via different means. When an organism derives its energy via electron transfer from light, it is called phototrophs. When organisms receive energy from the breaking of chemical bonds, they are called chemotrophs. 

Chemotrophs are of two types: organotrophs and lithotrophs. Organotroph examples include humans, fungi, prokaryotes, etc. and they derive energy from other organic sources, and form a vast majority of living species around us. Lithotrophs derive energy from inorganic compounds such as hydrogen sulfide, reduced iron compounds, etc. Examples of chemolithotrophs include plastids, giant tube worms, etc. The below table shows different classifications of microorganisms based on their energy sources. 

Source: BrainKart, n.d. 

Frequently Asked Questions (FAQs): What is the difference between lithotrophs and autotrophs?

What is the difference between photosynthesis and chemosynthesis?

Photosynthesis is a method used by plants where they use energy from sunlight to convert water from the soil and carbon dioxide from the air, to form glucose. Glucose is a type of sugar that provides plants energy and provides cellulose to build grow and build plant cell walls. 

Chemosynthesis refers to when plants or organisms acquire energy from chemical reactions in the environment, rather they use the energy from chemical reactions as their source of energy to form glucose. These organisms usually live in extreme conditions, an example of organisms that use chemosynthesis would include bacteria that live in active volcanoes. 

(Rutledge K. et.al., 2011)

Where are lithotrophs found?

Lithotrophs can be found in soil and aquatic environments wherever an appropriate energy source could be present. Most lithotrophs are autotrophs which means that they can grow in the absence of any organic material. Lithotrophic species are usually found amongst species of Bacteria and Archaea. Lithotrophs have an obvious and major impact on the sulfur, nitrogen, and carbon cycles in the biosphere.

For example, sulfur-oxidizing lithotrophs convert H2S to  SO and SO to SO4. Nitrifying bacteria can convert NH3 to NO2 and NO2 to NO3

Methanogenic archaea can strip electrons off of H2, add them to CO2 to form CH4 (methane).

References 

Anonim O. (2020, June 21). What is an autotroph example. Slide Share. Viewed on 02-01-2022. https://slidesharetips.blogspot.com/2020/06/what-is-autotroph-example_21.html 

BrainKart. (n.d.). Nutritional types of microorganisms. Microbiology 11th std. Viewed on 02-01-2022. https://www.brainkart.com/article/Nutritional-Types-of-Microorganisms_35239/ 

Gorane J. (2021, April 21). What are the differences between autotrophic and heterotrophic nutrition? CBSE Class Notes Online. Viewed on 02-01-2022. http://classnotes123.com/what-are-the-differences-between-autotrophic-and-heterotrophic-nutrition/ 

LibreTexts. (2021, February 17). Metabolic Lifestyles. Viewed on 02-01-2022. https://bio.libretexts.org/Courses/Mansfield_University_of_Pennsylvania/BSC_3271%3A_Microbiology_for_Health_Sciences_Sp21_(Kagle)/04%3A_Microbial_Diversity/4.03%3A_Representative_Groups/4.3.02%3A_Metabolic_Lifestyles 

Rutledge K., Ramroop T., Boudreau D., McDaniel M., Teng S., Sprout E., Costa H., Hall H., & Hunt J. (2011, January 21). Autotroph. Encyclopedic Entry. Resource Library. National Geographic Society. Viewed on 02-01-2022. https://www.nationalgeographic.org/encyclopedia/autotroph/#:~:text=An%20autotroph%20is%20an%20organism,they%20are%20sometimes%20called%20producers

Todar K. (n.d.). Ecology of Bacteria and Archaea. Overview of Bacteriology (page 5). Viewed on 02-01-2022. http://textbookofbacteriology.net/bacteriology_5.html#:~:text=Lithotrophs%20are%20found%20in%20soil,So%20to%20SO4.  

What was missing from this post which could have made it better?

Leave a Comment