Chemosynthetic bacteria oxidize inorganic compounds to obtain energy without using sunlight. Thiobacillus, Beggiatoa, Nitrobacter, and Nitrosomonas are the best examples of chemosynthetic bacteria.
Did You Know?
Unlike viruses, bacteria do not require any host for replication, as they have the ability to reproduce asexually.
Can you imagine life can exist deep in the sea in complete darkness? Doesn’t it sound surprising that life can thrive in 2,000 to 6,000 meters below the surface of the sea. At such depths, in extreme conditions, the existence of life in the form of a wide range of sea creatures is sure to keep anyone riveted. The living conditions generated in such extreme environment is due to the presence of chemosynthetic bacteria. These bacteria form the basis of existence of marine life in such severe conditions. The following sections provide useful information about chemosynthetic bacteria, for a better understanding.
What are Chemosynthetic Bacteria?
In simple words, these bacteria capture energy and make it available for everyone in the ecosystem thriving at the ocean floor. The bacteria essentially derive energy from chemical nutrients (inorganic compounds) through oxidation. Also referred to as autotrophs, the bacteria get energy from breaking chemical bonds during a chemical reaction. The energy released is then used by them to manufacture glucose (food).
Chemosynthetic bacteria are believed to be the first life-forms to appear on Earth. Although bacteria have been considered to be one of the most ancient organisms on Earth, the ones that are chemosynthetic are believed to be the oldest life-forms ever. These specialized bacteria might have been responsible for the very beginning of life on the Earth.
Types of Chemosynthetic Bacteria
As aforementioned, chemosynthetic bacteria use inorganic compounds to obtain energy and manufacture food. Depending upon the inorganic material involved in the oxidation process, they are classified into the following main types:
Nitrifying bacteria initiate oxidation of ammonium to nitrite, which is later oxidized to nitrates to obtain energy. Nitrates act as nutrients for plants and promote their growth. Nitrifying bacteria commonly occur in aquatic environment (freshwater, marine water, potable water). Their other habitats include sewage and soil. Nitrosomonas and Nitrobacter are some examples of chemosynthetic nitrifying bacteria.
NH4+ + 2O2 —> NO2– + 2H2O + energy.
2NO2– + O2 —> 2NO3– + energy
These bacteria reside at great depths below the surface of the sea, near the hydrothermal vents. Hydrogen sulfide seeps from these vents, which is oxidized by the bacteria to derive energy. Due to these bacteria, diverse ecosystems having innumerable species of marine animals flourish near hydrothermal vents. Thiobacillus and Beggiatoa are the two common species of sulfur bacteria.
2H2S + O2 —> 2S + 2H2O + energy
These bacteria thrive in iron-rich environment. They are found in abundance in wells, as there is adequate iron and other minerals such as manganese there. The bacteria are also present in streams, shallow aquifers, and soil.
These microorganisms obtain energy by converting ferrous iron to the ferrous state. It is a part of their metabolism, which enables them to derive energy and make food. Ferrobacillus and Gallionella are the most common species of iron bacteria.
4FECO3 + 6H2O + O2 —> 4Fe (OH)3 + 4CO2 + energy
Relationship Between Chemosynthetic Bacteria and Tubeworms
Tubeworms are one of the innumerable species of marine invertebrates residing near hydrothermal vents. Creatures like tubeworms having a habitat at such incredible depths is due to the presence of chemosynthetic bacteria.
In spite of having crushing deep-ocean water pressure and extreme temperature, tubeworms flourish in such hostile environment. This is because they support chemosynthetic bacteria, organisms that manufacture their own food. As bacteria reside inside the tubeworms, these creatures get a ready supply of food. With no digestive system present in these creatures, they fully depend on chemosynthetic bacteria for their nutrition.
The bacteria residing in the tubeworms also get a steady supply of hydrogen sulfide. This is because, the creatures readily absorb oxygen and hydrogen sulfide seeping from hydrogen vents. With both oxygen and sulfide present inside the creatures, the bacteria carry the process of oxidation. The energy liberated is then utilized by the bacteria for making food, excess of which is given to the tubeworms. A tubeworm provides shelter to millions of chemosynthetic bacteria, thereby ensuring that it is never shortage of food supply.
On the whole, light is not the only source of energy on which life on Earth depends. Photosynthesis, that occur in plants, is not the only way in which food is made. There are chemosynthetic bacteria that can also help sustain life on Earth. They do not use light, but use certain chemicals as an energy source and to make food. It is this process of chemosynthesis that has led to the development of marine ecosystems below the depths of light penetration.