Chemosynthesis: Definition, Equation, Function, And Types

Chemosynthesis Definition

Chemosynthesis is a biological process in which one or more carbon-containing molecules and nutrients are converted into organic matter using the oxidation of inorganic compounds as a source of energy, rather than sunlight as in photosynthesis.

Bacteria living in aphotic areas of the ocean are able to survive by chemosynthesis. The process uses energy from inorganic chemicals such as hydrogen gas, hydrogen sulfide, ammonia, or ferrous iron to convert them into organic matter such as sugars and amino acids.

Chemosynthesis Equation

Chemosynthesis is a process by which organisms use energy derived from chemical reactions to produce food. The equation for chemosynthesis varies depending on the energy source used.

For example, in hydrogen sulfide chemosynthesis, carbohydrates (CH2O) can be produced in the presence of carbon dioxide and oxygen:

CO2+ O2+ 4H2S → CH2O + 4S + 3H2O

Another example of a chemosynthesis equation involving hydrogen sulfide is:

18H2S+6CO2+3O2 → C6H12O6 +12H2O+18S

Chemosynthetic bacteria are capable of using different energy sources to produce food. Sulfur bacteria use sulfur compounds as an energy source, while metal ion bacteria use metal ions for chemosynthesis. Nitrogen bacteria use nitrogen compounds as an energy source.

Function of Chemosynthesis

Chemosynthesis is the biological conversion of one or more carbon-containing molecules and nutrients into organic matter using the oxidation of inorganic compounds as a source of energy, rather than sunlight, as in photosynthesis.

The function of chemosynthesis is to allow organisms to live without using the energy of sunlight or relying on other organisms for food. Chemosynthesis turns nonliving matter into the living matter by turning inorganic molecules into organic molecules.

Chemosynthesis occurs in environments where sunlight is not available, such as deep-sea hydrothermal vents and cold seeps. In these environments, chemosynthetic bacteria use the energy from chemical reactions to produce organic compounds that serve as food for other organisms.

For example, some species of tube worms have symbiotic relationships with chemosynthetic bacteria that live inside their bodies. The bacteria produce organic compounds that the tube worms use for nutrition.

Chemosynthesis plays an important role in ecosystems where sunlight is not available. It allows organisms to survive and thrive in environments that would otherwise be uninhabitable.

Types of Chemosynthetic Bacteria

Sulfur Bacteria

Sulfur bacteria are a type of chemosynthetic bacteria that use sulfur compounds as fuel sources for chemosynthesis. They oxidize sulfur compounds such as hydrogen sulfide, thiosulfates, and inorganic sulfur to produce organic matter.

In hydrogen sulfide chemosynthesis, solid globules of sulfur are produced instead of releasing oxygen gas while fixing carbon dioxide as in photosynthesis.

Sulfur bacteria carry out the oxidation of H2S, S, and other sulfur compounds to produce organic matter. These bacteria are found in various environments such as hot springs, deep-sea vents, and alpine meromictic lakes.

Metal Ion Bacteria

Metal ion bacteria are a type of chemosynthetic bacteria that use metal ions for chemosynthesis. Metal ions are essential for many reactions, but excess metals can be toxic. In bacteria, metal limitation activates pathways that are involved in the import and mobilization of metals.

Bacterial uptake of non-essential metals occurs through routes normally reserved for essential organic and inorganic ions, and transporters from several families are known to be involved.

Metal ions fulfill various essential roles within bacterial pathogens such as acting as necessary cofactors for cellular proteins, making them indispensable for both protein structure and function, and also fulfilling roles in signaling and regulation of virulence. Recently, scientists have discovered a type of bacteria that eats and gets its calories from metal.

Nitrogen Bacteria

Nitrogen bacteria are any bacteria that use nitrogen compounds in their metabolic process. While all of these bacteria use electrons from nitrogen compounds to create organic compounds, they can have very different effects on their ecosystem depending on what compounds they use.

Nitrogen bacteria can usually be divided into three classes:

1. Nitrifying bacteria:

Nitrifying bacteria are a type of chemolithotrophic organisms that get their energy from the oxidation of inorganic nitrogen compounds. They play a key role in the nitrogen cycle by converting atmospheric nitrogen into biologically usable forms in a process called nitrogen fixation.

Nitrifying bacteria are aerobic bacteria that use inorganic chemicals as an energy source and are important in the nitrogen cycle as converters of soil ammonia to nitrates, which are compounds usable by plants.

There are two types of nitrifying bacteria: ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Nitrifying bacteria carry out aerobic biological ammonia oxidation to nitrate, which is vital for assuring the purity of drinking water.

Nitrogenase catalyzes the breaking of the bond between two nitrogen atoms and is required by microorganisms that fix nitrogen. These microorganisms require 16 moles of adenosine triphosphate (ATP) to fix one mole of nitrogen gas into ammonia.

2. Denitrifying bacteria:

Denitrifying bacteria are a type of bacteria that use inorganic compounds, organic carbon compounds, and light as energy sources. They have been identified in over 50 genera with over 125 different species and are estimated to represent 10-15% of the bacterial population in water, soil, and sediment.

The dominant populations of denitrifiers appear to be organotrophs such as Pseudomonas and Alcaligenes. Denitrifying bacteria plays an important role in the nitrogen cycle by converting nitrates into nitrogen gas.

They require a very low oxygen concentration of less than 10%, as well as organic carbon for energy. Denitrification can remove NO3−, reducing its leaching to groundwater, and making it useful for treating sewage or animal residues with high nitrogen content.

3. Nitrogen fixing bacteria:

Nitrogen-fixing bacteria are microorganisms capable of transforming atmospheric nitrogen into fixed nitrogen, which are inorganic compounds usable by plants. They play an important role in the nitrogen cycle, accounting for more than 90% of all nitrogen fixation.

Nitrogen-fixing bacteria can be found in the soil and within the root nodules of some plants where they convert nitrogen gas in the atmosphere to ammonia. The reduction of molecular nitrogen (N2) into ammonia (NH3) or related nitrogenous compounds is called biological nitrogen fixation (BNF).

Nitrogen fixation occurs naturally as the nitric oxide by lightning and ultraviolet rays, but more significant amounts of nitrogen are fixed as ammonia, nitrites, and nitrates by soil microorganisms.


Methanobacteria is a class of archaeans in the kingdom Euryarchaeota that includes methanogens, which are bacteria that produce methane as a metabolic by-product. Methanobacterium is a genus of methanogenic bacteria that are nonmotile and live without oxygen.

They can use formate to reduce methane or live exclusively through the reduction of carbon dioxide with hydrogen. Methanobacteria is widespread in nature and can be found in mud, sewage, sludge, and hot springs.

They have several applications such as biomass conversion and energy production through the anaerobic digestion (AD) process. The methanobacteria have a relatively large number of Ni-dependent enzymes including some of the key enzymes in methanogenesis itself.

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