Chemosynthesis is a metabolic process in which inorganic substances are oxidized in contact with a carbon source, to produce organic substances that serve for the survival of the organism. Some organisms that use this process are sulfur or ferrous bacteria. The difference with photosynthesis is that chemosynthesis uses chemicals to obtain energy, while photosynthesis uses light.
Living beings have a wide variety of mechanisms to survive and keep their basic functions functioning. We know that plants use sunlight to produce their food, but did you know that there is another group that also makes its own food, but it does so from chemicals without needing light? These are chemosynthetic organisms. In this Evidence Network article we explain more about what chemosynthesis is, its phases, organisms and difference with photosynthesis.
What is chemosynthesis
Chemosynthesis is an anabolic biological process, that is, it manufactures molecules from simple chemical compounds to form more complex molecules. By analyzing the word chemosynthesis, we can easily understand that it is a process of synthesis of chemical compounds. In the process, carbon-rich molecules are used along with the oxidation of inorganic compounds to produce organic matter. It is a metabolic process, that is, it is necessary for the survival of the organism, both to manufacture molecules and to obtain energy.
Simply put, in chemosynthesis inorganic molecules are transformed into organic molecules, to be integrated into the metabolism.
Phases of chemosynthesis
Chemosynthesis is carried out in two phases, which we detail below.
Phase I: Obtaining energy
This is the first step of chemosynthesis, and this is when the generation of ATP, the energy molecule, takes place in this phase.
To do this, inorganic compounds are oxidized, that is, they do not have carbon, which are present in the body’s environment. Some of them are sulfur, methane, ferrous iron, ammonia, hydrogen or nitrites. The oxidation process implies that these molecules lose electrons that enter the electron transport chain, where ATP is generated. In this step, the inorganic compound will be transformed.
Phase II: CO2 Fixation
It is the second part of chemosynthesis. Here the energy obtained is used to transform inorganic substances. It is at this moment where CO2 or methane, which are the carbon sources, are fixed to organic matter through the Calvin cycle. The result will be the transformation into carbohydrates and amino acids, which are what chemosynthetic organisms need to survive.
Examples of chemosynthetic organisms
In general terms, they are grouped together with certain bacteria and algae, and many of them live in extreme environments. Below, we present some of them.
Hydrogenous bacteria
They are those that oxidize hydrogen compounds. They use molecular hydrogen (H₂) as an energy source, which reacts with oxygen to form water. This reaction releases energy, which is used for the synthesis of essential organic compounds. They are found in environments with low oxygen concentration and the presence of gases, such as underground springs or deep marine sediments.
sulfur bacteria
These are organisms that oxidize sulfur compounds, which in many cases are formed in the decomposition of organic matter. These compounds, together with CO2, will form carbohydrates and sulfur, the former being those used by the bacteria to carry out its basic functions.
They are frequently found in discharge waters with a characteristic sulfur aroma, as well as on the seabed of hydrothermal springs, or among the accumulation of mud.
An example is the symbiotic bacteria that live in the giant tube worm (Riftia pachyptila), which lives in oceanic hydrothermal springs, where light does not reach and the temperature is extremely high. These bacteria use hydrogen sulfide that comes from hydrothermal sources as energy sources, and as a result of chemosynthesis, they produce, in addition to the carbohydrates and amino acids they require to survive, sulfur as a byproduct. These bacteria carry out the process of obtaining organic matter so that the giant tube worm can take advantage of them to survive.
Nitrifying bacteria
They are those that oxidize ammonia first to nitrites and then to nitrates, which are extremely important for plants to grow. For example, these nitrogen compounds help legumes produce proteins.
Some examples of nitrifying bacteria species are Nitrobacter spp., and Nitrosomonas spp.
ferrous bacteria
They oxidize ferrous oxide to ferric oxide, and an example is Leptospirillum ferrooxidans. As a byproduct they form ferric oxide, known as oxide. They contribute to the deterioration of pipes, and can be identified by a rotten smell.
Difference between photosynthesis and chemosynthesis
Both photosynthesis and chemosynthesis are anabolic processes in which an organism produces its own energy, but the difference between the two is that photosynthesis uses light energy to generate energy, while chemosynthesis uses chemical energy for this purpose.
In this other Evidence Network article you can learn more about Photosynthesis: what it is, phases and importance.
Importance of chemosynthesis
Chemosynthesis was the first type of metabolism that existed on earth. If it were not for this process, life would not exist.
It is important at the ecosystem level because it uses the reduced substances that heterotrophic living beings emit as waste to carry out their metabolization process. This means that they are recycling inorganic compounds and closing the cycle that sustains other living beings. For example, nitrifying bacteria will use ammonia from animal carcasses into nitrates useful for plants. Also, they help maintain the nitrogen and hydrogen cycle, both essential for life.
On the other hand, they can improve environmental conditions. For example, there are some bacteria that nitrify the soil, leaving this element bioavailable for plants.
If you want to read more articles similar to Chemosynthesis: what it is, phases, organisms and difference with photosynthesis, we recommend that you enter our Biology category.
- Lauría Baca, L. (2015). Biology 1. Spain: Larousse – Grupo Editorial Patria.
- Gama Fuertes, M. dl Á. (2007). Biology 1 – Sep “A Constructivist Approach”. Mexico: Pearson Education.
