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Primary nutritional groups

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Title: Primary nutritional groups  
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Subject: Metabolism, Landscape ecology, Autotroph, Biomass (ecology), Heterotroph
Collection: Physiology, Trophic Ecology
Publisher: World Heritage Encyclopedia

Primary nutritional groups

Primary nutritional groups are groups of electron transport chain fermentation is often referred to as substrate-level phosphorylation.


  • Primary sources of energy 1
  • Primary sources of reducing equivalents 2
  • Primary sources of carbon 3
  • Energy and carbon 4
  • Primary metabolism table 5
  • Mixotrophs 6
  • Examples 7
  • See also 8
  • References 9

Primary sources of energy

Simplified flowchart for determining if an organism is an autotroph, heterotroph or a subtype.

Phototrophs: Light is absorbed in photo receptors and transformed into chemical energy.
Chemotrophs: Bond energy is released from a chemical compound.

The freed energy is stored as potential energy in ATP, carbohydrates, lipids or proteins. Eventually, the energy is used for life processes as moving, growth and reproduction.

Some bacteria can alternate phototrophy and chemotrophy, depending on availability of light.

Primary sources of reducing equivalents

electron donor.
Lithotrophs: Inorganic compounds are used as electron donor.

The electrons from reducing equivalents are needed by both phototrophs and chemotrophs, to keep running reduction-oxidation reactions that transfer energy. The electron donors are taken up from the environment.

Organotrophic organisms are often also heterotrophic, using organic compounds as sources of electrons and carbon at the same time. Similarly, lithotrophic organisms are often also autotrophic, using inorganic sources of electrons and CO2 as inorganic carbon source.

Some lithotrophic bacteria can utilize diverse sources of electrons, depending on availability of possible donors.

Primary sources of carbon

metabolized to get carbon for growth and development.
Autotrophs: Carbon dioxide (CO2) is used as source of carbon.

Energy and carbon

Yellow fungus
Classification of organisms based on their metabolism
Energy source sunlight photo-   -troph
Preformed molecules chemo-
Electron donor organic compound   organo-  
inorganic compound litho-
Carbon source organic compound   hetero-
carbon dioxide auto-

A chemoorganoheterotrophic Herbivores and carnivores are examples of organisms that obtain carbon and electron reactions from living organic matter.

Chemoorganotrophs are glucose), fats and proteins.[2]

All Eukaryotes are generally easy to categorise. All animals are heterotrophic, as are fungi. Plants are generally photoautotrophic. Some eukaryotic microorganisms, however, are not limited to just one nutritional mode. For example, some algae live photoautotrophically in the light, but shift to chemoorganotrophy in the dark. Even higher plants retained their ability to respire heterotrophically on the starch at night which had been synthesised phototrophically during the day.

facultative and switch from one mode to the other, depending on the nutrient sources available.

See also


  1. ^ Brock Biology of Microorganisms Definitions of metabolic strategies to obtain carbon and energy
  2. ^ Kenneth Todar (2009). "Todar's Online Textbook of Bacteriology". Nutrition and Growth of Bacteria. Retrieved 2014-04-19. 
  3. ^ Kelly, DP; Julie Mason; Ann Wood. Energy Metabolism in Chemolithotrophs. Springer. pp. 186–187. 
  4. ^ Y. Kellermann, Gunter Wegener, Marcus Elvert, Marcos Yukio Yoshinaga, Yu-Shih Lin, Thomas Holler, Xavier Prieto Mollar, Katrin Knittel, and Kai-Uwe Hinrichs. Autotrophy as a predominant mode of carbon fixation in anaerobic methane-oxidizing microbial communities. PNAS 2012, vol. 109 no. 47.
  5. ^ Yafremava LS, Wielgos M, Thomas S, Nasir A, Wang M, Mittenthal JE, Caetano-Anollés G: A general framework of persistence strategies for biological systems helps explain domains of life. Front Genet 2013; 4:16; p.8
  6. ^ R. Rippka Photoheterotrophy and chemoheterotrophy among unicellular blue-green algae Archives of Microbiology; Volume 87, Number 1 / March, 1972; doi:10.1007/BF00424781
  7. ^ Alexander Eiler Evidence for the Ubiquity of Mixotrophic Bacteria in the Upper Ocean: Implications and consequences Appl Environ Microbiol. 2006 December; 72(12): 7431–7437; doi:10.1128/AEM.01559-06.
as a carbon source. Fungi are 2, since they use light as an energy source, water as electron donor, and COphotoautotrophic All sorts of combinations may exist in nature. For example most cyanobacteria are


[7] Such [6] Chroococcales Some, usually unicellular, organisms can switch between different metabolic modes, for example between photoautotrophy, photoheterotrophy, and chemoheterotrophy in


  • Some authors use -hydro- when the source is water.
Carbon source Name Examples
Sun Light
Carbon dioxide
Carbon dioxide
Photolithoautotroph Embryophyta, algae
Chemoorganoheterotroph Metazoa, Fungi
Carbon dioxide
Chemoorganoautotroph Anaerobic methanotrophic archaea[4]
Carbon dioxide
Chemolithoautotroph Nitrobacter[5]

Primary metabolism table

[3] The terms


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