All lifeforms on earth can be classified into groups based on their mode of nutrition. Plants are classified as autotrophs (more specifically photoautotrophs) because they can harness sunlight and convert it into useable energy. Animals are classified as heterotrophs because they rely on other organic sources (such as plant or animal matter) for their energy needs. Another class of organisms that can obtain energy liberated from chemical reactions are called chemotrophs.
What Are Chemoautotrophs?
Photosynthetic organisms are also termed as photoautotrophs because they can synthesise their own energy using photosynthesis. Similarly, chemoautotrophs are organisms that, in addition to obtaining energy from chemical reactions, can synthesise crucial organic compounds from gases like carbon dioxide. Sunlight is the primary energy source for autotrophs, chemoautotrophs, on the other hand, use hydrogen sulphide, ammonia and other compounds as an energy source.
Where Are Chemotrophs Found?
Chemotrophic organisms are generally extremophiles, found in hostile environments. These organisms can live on the ocean floor, where sunlight cannot penetrate. Temperatures are also frigid, usually hovering between 0 to 3-degree Celcius.
In these conditions, the only viable source of energy is the deep-sea hydrothermal vents. These are volcanic vents spewing out chemical-rich fluids from the sea bed. Hence, compared to the other parts of the seabed, areas around these hydrothermal vents are considered a biological hotspot. Entire communities of various lifeforms can be observed, living isolated from the sun and the outside world.
Unsurprisingly, these environments are hazardous for every other type of lifeform except extremophiles. For instance, hydrogen sulphide is extremely lethal to most organisms, but extremophiles thrive on this toxic compound. It has also been theorised that life originated from such extreme environments, and the very first types of life may have been chemotrophs.