7: Nutrient and Energy Resources
- Page ID
- 131850
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“Microbial life exists in all the locations where life can survive, that would mean all the locations that have a chemical energy supply and that are at a temperature below the maximum one to which microbes can adapt”
—Thomas Gold, PNAS 1992
“Life will find a way”
—Michael Crichton, Jurassic Park
The abundance and types of nutrient and energy resources in an environment can influence many aspects of that environment’s microbial activity. Nutrient and energy resource availability helps determine what types of microbial reactions can be present and the extent to which microbes driving those reactions can be active. Nutrient and energy resource availability also affects the composition of the microbial community. If the chemicals an organism needs from the environment for their metabolism are not available, then that organism cannot live there. However, other organisms may have different needs and can survive or even thrive in that same environment.
For the purposes of this chapter, we will consider energy sources to be sources of electrons. For phototrophic organisms, electrons are discharged when light is absorbed by specialized pigments such as chlorophyll (Section 4.5). So, we can think of light as their ultimate energy source. For chemotrophs, we can consider their electron donors to be their energy sources.
- 7.1: Nutrients
- Sources of the major macronutrients (carbon, nitrogen, and phosphorus) for microbial organisms.
- 7.2: Extracellular enzymes
- Overview of how extracellular enzymes help supply microorganisms with nutrients and energy resources.
- 7.3: Nutrient stoichiometry
- The roles played by nutrient stoichiometry in controlling microbial populations, including acting as growth-limiting factors and influencing the identity of the species able to grow in an environment.
- 7.4: Energy sources for phototrophs
- Limiting effects of light penetration depth on environments where phototrophic microorganisms can be found. Alternative sources of EM radiation that have the potential to provide phototrophs with energy.
- 7.5: Energy sources for chemotrophs
- Classification of chemotrophs according to the organic or inorganic origin of their electron donors. Discussion of possible sources of these electron donors, including organic material, reduced inorganic components of minerals, mantle degassing, serpentinization, water radiolysis, silica-based radical reactions, and atmospheric trace gases.
- 7.6: Electroactive organisms
- Discussion of electroactive microorganisms, which are able to exchange electrons from their extracellular environment, and how this characteristic may complicate the previously defined energy source categories.