Most bacteria get their nutrients by breaking down the organic matter of things that once lived, classifying them as heterotrophs. This includes bacteria in the soil and those that make us sick.
This is an effective classificationthe most consuming or decomposing bacteria.And these bacteria are immensely important for our ecosystems.
Other bacteria such ascyanobacteria, are autotrophs and are therefore able to obtain their energy without eating other organisms – in the case ofcyanobacteriaand other photosynthetic bacteria get their energy from the sun.
Unlike photosynthetic bacteria, chemosynthetic bacteria do not obtain their energy from the sun through photosynthesis, but are able to use chemical energy stored in inorganic compounds to release energy!
Chemosynthetic bacteria are therefore considered autotrophicmost frequentlyget their carbon from carbon dioxide.
However, although less common, chemosynthetic bacteria can (at least in theory) also be heterotrophic if they use chemical energy but derive their carbon from organic compounds - but are generally no longer considered fully chemosynthetic!
Let's dig deeper into what exactly these bacteria do and where to find them next!
What are chemosynthetic bacteria?
Chemosynthetic bacteria are a type of bacteria that do not break down organic matter for energy. Instead, they use inorganic chemicals from the environment to generate energy and build organic molecules.
chemosyntheticOrganisms are also known asChemolithotrophe.
Instead of feeding on othersChemolithotropheuse a process known as chemosynthesis, in which inorganic molecules are converted into organic molecules, from which their cellular components are built.
Inorganic molecules consumed as energy by chemosynthetic bacteria are generally based on iron or hydrogen, such as ammonia (denitrifying bacteria) or hydrogen sulfide (sulphur bacteria).and its carbon source is carbon dioxide. This makes chemosynthetic bacteria completely self-sufficientautotroph.
They can harvest energy where there are no other sources of energy such as the sun and other living organisms. As such, they are often found in extreme environments such as deep vents, volcanic craters, and hot springs.
Since chemosynthetic bacteria can live in environments where photosynthesis is not possible, they are the main primary producers.
Chemosynthetic bacteria are very important for ecosystems that do not photosynthesize and do not support many other forms of life, such as in the dark of the deep sea!
In fact, other organisms in these deep-sea environments are highly dependent on chemosynthetic bacteria for their survival, and some even feed on them as their sole food source.
Giant tubeworms get their energy from chemosynthetic bacteria!
Giant tubeworms live deep in the ocean that do not receive sunlight or other forms of energy from above. Therefore, they only feed on the carbon produced by chemosynthetic bacteria to survive.
Chemosynthetic bacteria live in the burrows of giant tubeworms and obtain energy for themselves by breaking down sulfur compounds found near hydrothermal vents.Worms absorb this energy from chemosynthetic bacteria, which ingest their organic building blocks when they die!
The relationship between giant tubeworms and chemosynthetic bacteria is beneficial to both organisms. Bacteria get a place to live and worms get energy to survive! Win!
Can chemosynthetic bacteria also be heterotrophs?
Most bacteria and animals get their energy and carbon by breaking down the organic molecules of other living organisms, but this defines them as heterotrophschemosynthetic bacteria are almost always autotrophic because they "self-sustain" through carbon dioxide.
If complex organic molecules were plentiful, they too could get their energy from fermentation without the need for inorganic molecules—back thenWhy do chemosynthetic bacteria prefer inorganic molecules?
Chemosynthetic bacteria, especially those living in extreme environments, use carbon dioxide as a source of carbon, probably because there are few living organisms that could provide more complex organic molecules.and why competing for food with heterotrophs is a bad strategy.
Also, inorganic molecules are often better electron acceptors than organic ones, and fermentation residues (like ethanol and organic acids) are often toxic and eaten by competing bacteria!
An example of heterotrophic chemosynthetic bacteria are the bacteria ofDesulfovibriGender.
Originally, these bacteria were thought to be fully autotrophic and could only get their carbon from carbon dioxide.it later turned out that adding organic molecules from the yeast extract made them grow even better.
Other organisms suffering from a similar identity crisis are theEuglena protists who can function like plants and animalsand get yoursEnergy through photosynthesis.
However, when these examples occur, the discussion begins as to whether such organisms are autotrophic or heterotrophic!
It could be argued that they are still autotrophic as this is the "simpler" or basic mode of carbon uptake, actually autotrophic but theDesulfovibri The bacteria mentioned in the example above are now referred to as heterotrophs rather than autotrophs.
Are chemosynthetic bacteria decomposers?
Chemosynthetic bacteria are heterotrophic autotrophs and can therefore also be decomposers, as if deriving their energy from organic matter. However, if they get their carbon from carbon dioxide, they are not classified as decomposers.
Decomposers are defined by their ability to eat the remains of other living organisms, classifying them as heterotrophs.
Most chemosynthetic bacteria do not eat other organisms or their decaying bodies, so they are not decomposers or consumers, but strain producers.
However, some chemosynthetic bacteria derive their energy from sulfur released from bones and decaying bones on the sea floor, and are therefore involved in recycling dead material into organic materials that can be used by the upper trophic layers.
And while some chemosynthetic bacteria are primary producers (like plants) because they can convert inorganic molecules (like CO2) directly into organic molecules that other organisms can feed on, others eat organic compounds to get their building blocks of carbon.
Chemosynthetic bacteria, which get their energy from inorganic compounds but have little more than carbon dioxide as a carbon source, can be considered decomposers if they feed on dead animals or plant matter.
Today,most microbes and animaEUOrganisms on Earth are indeed heterotrophs, breaking down the organic matter left behind by other dead organisms such as animals and plants!
In that regardChemosynthetic bacteria are at the bottom of the food chain/pyramid because they form the very important basis for heterotropic life on Earthto arise and evolve into all the organisms we know today!
Microorganisms such as e.gBacteria and fungi are the most important "cleaners" of ecosystemsin the world today!
How do chemosynthetic and photosynthetic bacteria differ?
The difference between chemosynthetic bacteria and photosynthetic bacteria is that chemosynthetic bacteria use chemosynthesis for energy and photosynthetic bacteria use photosynthesis.
The key difference between chemosynthesis and photosynthesis is that photosynthesis uses sunlight to produce food whereas chemosynthesis uses inorganic chemicals from the environment.
During photosynthesis, the sun's energy is used to produce glucose from carbon dioxide and water. In chemosynthesis, inorganic compounds are broken down with the release of energy.
This energy can be used to power the cell or to make ATP, a molecule that cells use for energy.
Another difference is that many chemosynthetic bacteria are extremophilic, most are anaerobic, and many live in complete darkness!
How did early heterotrophs produce energy?
In the beginning there was only chemosynthesis, but how did heterotrophs come about?
It is very likely that chemosynthetic bacteria and archaea are the organisms most closely resembling first life on Earth!
Chemosynthetic bacteria used their energy to grow, thereby forming new masses of organic molecules that other organisms evolved to feed on.– these organisms were the first heterotrophs!
The first primitive heterotrophs were probably bacteria that fed on the first organic compounds produced by chemosynthetic bacteria. They were anaerobic as there was no oxygen on Earth at the time.
Due to the lack of oxygen, they would have to use another electron acceptor such as sulfur for anaerobic respiration to take place.
Alternatively, early primitive heterotrophs may also have used fermentation for energy.
Fermentation is the process where the metabolized organic compound is also used as the final electron acceptor., resulting in residues such as ethanol, methane or lactic acid.
With the advent of photosynthesis, oxygen began to fill the atmosphere, making it easier for heterotrophs to place their respiratory electrons in highly electron-hungry oxygen molecules rather than larger organic compounds.
Are archaebacteria autotrophic or heterotrophic?
Archaeacan be autotrophs and heterotrophs. Archaea are metabolically very diverse, allowing them to use a variety of different methods to generate energy.
Some archaea use chemosynthesis as autotrophs, while others consume organic material for energy and are therefore heterotrophs. Archaebacteria are often classified as methanogenic because they produce methane as part of their metabolism.
Archaea can also walka primitive form of photosynthesisbased on complexes based on Mg-tetrapyrrole. This type of photosynthesis is different from that of plants and does not produce oxygen gas.