Chemosynthetic Bacteria: Everything You Need To Know

On face value, the words “chemosynthetic bacteria” might seem dull, but in actuality they are both fascinating and useful microorganisms that create and maintain life in a lot of interesting ways.

Chemosynthetic Bacteria: Everything You Need To Know

But what exactly are chemosynthetic bacteria, and how exactly might we classify them? 

Discovering Chemosynthesis

Whilst there is little information about the actual discovery of these kinds of bacteria, the official term of the process, “chemosynthesis”, was coined by Wilhelm Pfeffer in 1897. 

He was a German botanist and plant physiologist, and although his original definition would now be referred to as “chemolithoautotrophy”, due to his description of energy production through the oxidation of inorganic substances in relation to autotrophy, this led the groundwork for modern technical understanding of the process. 

Chemosynthetic Bacteria: The Facts

Chemosynthetic bacteria are organisms that gain their energy from inorganic molecules, by converting them into organic substances. 


These inorganic molecules can be ammonia, molecular hydrogen, sulfur, hydrogen sulfide, and ferrous iron, and they get energy from them through oxidation, stimulating the production of organic compounds that they can utilize in order to survive. 

This differs from other organic bacteria and plant life, which has the ability to use photosynthesis for food. However, without the sun, this is not an option for chemosynthetic bacteria. 


Most chemosynthetic bacteria live in environments which have little to no sunlight.

These environments would normally be inhospitable to most organic lifeforms, but the unusual and fascinating nature by which they obtain nutrients and food means they can flourish where others might not.

They can be found especially in remote areas, such as the arctic and antarctic oceans, or buried deep in the ice where the sunlight cannot permeate. They have also been discovered several meters into the Earth’s crust. 


Their unusual manner of attaining food and nutrients means that chemosynthetic bacteria are chemoautotrophs. 

An autotroph is an organism that is able to derive food and nourishment from simple inorganic substances, such as carbon dioxide.

Chemoautotrophs get their name because they are able to perform the same process on less commonly occurring chemical substances found in some of the most inhospitable environments. 

Chemoautotrophs can fall into two distinct categories: chemoorganotrophs, and chemolithotrophs. 

Chemoorganotrophs are organic molecules, whereas chemolithotrophs are characterized as being inorganic in composition. 

The latter in particular are incredibly important to their attributed ecosystems, as they are able to convert carbon dioxide to glucose through a process called the Calvin cycle. This is the dark phase of photosynthesis, wherein carbon fixation, reduction, and regeneration occur.

Fixation sees the absorption of carbon dioxide, reduction sees the transfer from carbon to simple sugars (or glucose), and regeneration sees the implementation of the remaining carbon and other byproducts in fortifying and revitalizing the physiology of the plant/bacterial form. 


Like most bacteria, chemosynthetic bacteria reproduce through a process called binary fission, which sees the original form divide into two or more parts.

This is the reason that bacteria can multiply at an exponential rate, and why species of bacteria outnumber the numbers of other sentient life on Earth by an almost incalculable amount. 

Different Methods Of Attaining Energy 

The sheer difference between chemoautotrophs and other forms of organic life is staggering. 


Most plant life, algae, and even some forms of bacteria rely on the sunlight for their energy, which occurs through photosynthesis. This makes them phototrophs, as their energy derives directly from the sun’s heat and light. 

The process of photosynthesis involves plants absorbing light energy from the sun, carbon dioxide from the air, and minerals and water from the ground. 

For photosynthesis to occur, there needs to be sunlight and chlorophyll in the leaves of a plant.

During photosynthesis, the chlorophyll converts carbon dioxide and water within the plant into oxygen and glucose. It is this glucose that becomes a necessary source of food and fuel for the plant. 

Photosynthesis is important, as it provides all living organisms with oxygen, including us. And thus, without photosynthesis, life as we know it would not be possible. 

These operate at the first stage of the food chain, as they can produce their own food, albeit with the help of inorganic substances, and act as the base food source for sustaining the rest of the food chains within a specific ecosystem. 


Heterotrophs are organisms which consume other plants and animals in order to survive. The term derives from the Greek word hetero (meaning “other”) and trophe (meaning “nourishment”). 

Most organic creatures on Earth are heterotrophs, including humans, and they can be found all the way down to the level of bacteria. 

Heterotrophs also benefit from photosynthesis. Obviously it is important for us, because of our need for oxygen to live, but also because photosynthesis is responsible for the continued creation of our primary food sources, i.e. animals and plants. 

Heterotrophs occupy the second and third stages of a food chain within a specific ecosystem.

The heterotrophs at the second stage rely on the phototrophs (like plant life) to survive, whilst the heterotrophs at the third stage of the food chain generally rely on a diet of one or both. 

Hetero Vs Photo Vs Chemo

It is for these reasons alone that chemoautotrophs are so unusual within the wider global ecosystem, as the way they operate seems to defy, or at the very least deviate, from what we know to be true of most forms of life. 

Of course, life might be too strong a term for this level of bacteria. As far as we know, they do not possess any sentience, and the processes they undergo are more in line with naturally occurring chemical reactions than what could be called “feeding”. 

However, they are fascinating nonetheless, and they play a major part in the wider global narrative. 

Chemosynthesis Vs Photosynthesis

In terms of these processes, there are several key differences, some of which we have already touched upon through this article. 

All life on Earth requires the transition and transferral of inorganic compounds to organic compounds in order to create food, nutrients, and energy for organisms. 

Whilst both of these processes operate in different ways, they essentially achieve the same goal, albeit for different organisms in different environments. 

Places where there is plenty of sunlight facilitate photosynthesis, allowing plants to thrive and flourish, and other creatures to feast on them as food. 

Alternatively, environments where there is little to sunlight require chemosynthesis to convert inorganic (or unsuitable) chemical substances, such as ammonia and ferrous iron, into usable organic compounds, such as nitrogen and oxygen. 

This can then facilitate the growth of algae and some plant life, and create a somewhat thriving ecosystem in environments which otherwise shouldn’t be able to host life. 

The Importance Of Chemoautotrophs 

Autotrophs are called as such because they are capable of producing their own food and energy using chemicals in their surrounding environments.

Because of this, they are generally the foundations for food chains, and as such are incredibly important for the wider ecosystems as a whole. 

For Plant Life

Whilst chemoautotrophs generally occur in environments where plant life cannot exist (due to the lack of sunlight), some do occur amongst plants, and these are necessary tools for “fixing” the nitrogen in the water. 

This is done by oxidizing ammonia, which then becomes nitrate, a viable source of nutrients which can then be consumed by plants.

The consumption of nitrogen allows plants to make amino acids and proteins, which are important to not only their existence, but also the existence of the wider ecosystem. 


Chemosynthetic bacteria play a wider important role in global ecology, as they are capable of breaking down plant and animal matter into core components, such as nitrogen, which can then be utilized in the sustenance of other lower organisms. 

Energy Pyramids

Chemoautotrophs form the foundation of energy pyramids in ecosystems where photosynthesis cannot happen as readily.

Without the presence of chemoautotrophs, there would be no possibility of life being able to sustain itself in environments where the sun’s light cannot reach. 

An example of this is the presence of life in deep sea hydrothermal vents, which occur at depths so deep that no light can occur.

Their presence and continued study has also led scientists to speculate that chemoautotrophs could be the main foundations of life and energy on planets deprived of sunlight, such as the distant planetary bodies at the very edge of our solar system. 

The Origin Of Life

Some speculate that chemoautotrophs were the original source of life on our own planet, as there would have been a need for organisms that didn’t require organic matter to survive. 

This would then form the foundation for more complex species who feed on organic matter, allowing the evolutionary process of life on Earth to begin and continue. 

Of course, there are other environmental elements involved, such as levels of oxygen in the air, the amount of sunlight and ambient temperatures we are exposed to and others.

But this could go some way to explain why other planets in our solar system do not have the same levels of complex life as we do. 

This theory is supported by the presence of “extremophiles”. These are the chemoautotrophs which are capable of existing in some of the most hazardous and inhospitable environments on the planet, such as in highly acidic water, or in hydrothermal vents. 

The thinking goes that if they are capable of surviving in these environments, and even thriving without any sunlight or organic substances to survive on, then perhaps they could have survived during the beginnings of life, when the Earth was in its infancy. 

Examples Of Chemoautotrophs

Of course, within nature, there are several different examples of chemoautotrophs, some more common than others. 


These are a genus of nitrogen “fixing” bacteria, which convert ammonia into nitrogen through the process of oxidation. 

They are vital for forming amino acids and proteins in plant life, and are one of the more commonly found chemosynthetic bacteria in remote, relatively sunless environments where plants are still able to be found. 

Most plants cannot oxidize their own nitrogen, and as such these bacteria are incredibly important to certain environments where photosynthesis isn’t an option. 

Nitrogen fixation is an important part of farming, as most crops aren’t able to produce or oxidize their own nitrogen. As such, farmers either need to ensure there are plenty of nitrosomonas in their soil, or add nitrogen manually during feeding. 

Iron Bacteria

These are bacteria found around oxidizing ferrous iron which has been submerged in water. 

Somewhat unusually, their “diet” of iron means that they can survive in water with some of the highest concentrations possible – surviving in environments where such levels of iron would kill any other living thing. 

As such, they are generally found in iron-rich wells, hot springs, and rivers, and as such are thought of as pests due to the residue their oxidation process leaves behind – especially in unfiltered well water. 

However, some industries, such as iron mining, are looking at ways to utilize iron bacteria to oxidize and attain iron ore which would otherwise be inaccessible to human miners, either due to excess water or other environmental and logistical reasons. 


These are bacteria which produce methane, and gain energy from the electrons found in hydrogen gas. Through this process they produce methane and other organic substances, making them important parts of their respective ecosystems. 

They are generally found at the bottom of the ocean, and they have the power to create large methane bubbles beneath the ocean floor.

A similar thing happens in swamps and on marshlands, and methanogens are responsible for producing the “swamp gas” commonly associated with these areas. 

They can also strangely be found in the stomachs of cows, which would go some way to explain the level of methane produced by cows through the expelling of gas. They can even be found in some humans, given the optimal chance and appropriate digestive conditions. 

Methane is a powerful greenhouse gas, and has the potential to trap and store much more solar energy than other substances such as carbon dioxide. This is the reason many environmentalists are concerned about the effects of the growing beef industry on the environment. 

The more cows are reared, the more methane is expelled, which will in turn heat the atmosphere to dangerous levels.

Producing less cows would produce less methane, and as such, scientists believe this would halt or reverse some of the effects of man-made climate change. 

Final Thoughts

And there we have it, everything you need to know about chemosynthetic bacteria, the process of chemosynthesis, and the wider importance of it to the global ecosystem. 

Whilst this all may seem complex, what can be taken away is the sheer importance of chemosynthetic bacteria, or chemoautotrophs, to essentially conditioning the chemical composition of the most inhospitable environments from the inorganic to the organic, furthering growth, energy transfer, and ultimately the process of Earthly evolution. 

It’s true what they say, big things really do come in small packages!

Jennifer Dawkins

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