Microbial Metabolism

Microbial metabolism is the means by which a microbe obtains the energy and nutrients (e.g. carbon) it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe’s ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.

All microbial metabolisms can be arranged according to three principles:
How the organism obtains carbon for synthesizing cell mass
How the organism obtains reducing equivalents used either in energy conservation or in biosynthetic reactions
How the organism obtains energy for living and growing

1. How the organism obtains carbon for synthesizing cell mass:
Autotrophic – carbon is obtained from carbon dioxide (CO2)
Heterotrophic – carbon is obtained from organic compounds
Mixotrophic – carbon is obtained from both organic compounds and by fixing carbon dioxide

2. How the organism obtains reducing equivalents used either in energy conservation or in biosynthetic reactions:
Lithotrophic – reducing equivalents are obtained from inorganic compounds
Organotrophic – reducing equivalents are obtained from organic compounds

3. How the organism obtains energy for living and growing:
Chemotrophic – energy is obtained from external chemical compounds
Phototrophic – energy is obtained from light