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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.
An example of hydrogenotrophy is performed by carbon dioxide-reducing organisms [1] which use CO 2 and H 2 to produce methane (CH 4) by the following reaction: CO 2 + 4H 2 → CH 4 + 2H 2 O Other hydrogenotrophic metabolic pathways include acetogenesis , sulfate reduction , and other hydrogen oxidizing bacteria .
The exact mechanism is still a topic of debate but the most widely accepted theory is that the archaea use the reversed methanogenesis pathway to produce carbon dioxide and another, unknown intermediate, which is then used by the sulfate-reducing bacteria to gain energy from the reduction of sulfate to hydrogen sulfide and water.
These bacteria use reduced chemical species, most often sulfur, as sources of energy to reduce carbon dioxide to organic carbon. [11] The chemolithotrophic abundance in a hydrothermal vent environment is determined by the available energy sources; different temperature vents have different concentrations of nutrients, suggesting large variation ...
Lithoheterotrophs do not have the ability to fix carbon dioxide and must consume additional organic compounds in order to break them apart and use their carbon. Only a few bacteria are fully lithoheterotrophic. Lithoautotrophs are able to use carbon dioxide from the air as a carbon source, the same way plants do.
During advanced stages of organic decay, all electron acceptors become depleted except carbon dioxide. Carbon dioxide is a product of most catabolic processes, so it is not depleted like other potential electron acceptors. Only methanogenesis and fermentation can occur in the absence of electron acceptors other than carbon.
One particular flavobacterium cannot reduce carbon dioxide using light, but uses the energy from its rhodopsin system to fix carbon dioxide through anaplerotic fixation. [8] The flavobacterium is still a heterotroph as it needs reduced carbon compounds to live and cannot subsist on only light and CO 2. It cannot carry out reactions in the form of
Autotrophs use energy from sunlight (photoautotrophs) or oxidation of inorganic compounds (lithoautotrophs) to convert inorganic carbon dioxide to organic carbon compounds and energy to sustain their life. Comparing the two in basic terms, heterotrophs (such as animals) eat either autotrophs (such as plants) or other heterotrophs, or both.