How do bacteria get energy? How do bacteria get their food?

The way the bacteria get energy differs from bacterial species to species. Their nutrition and energy metabolism differs between the diversity of the various bacterial species.

Bacteria get energy by nutrition and then by their cellular metabolism. Their cellular metabolism is a combination of chemical reactions that are spontaneous and release energy for their survival, growth, and cell maintenance.

To carry out the metabolism in their cell, just in order to transport, synthesize, and breakdown the nutrients and molecules that they have derived from their nutrition, they do also require the use of energy that was produced during the previous cell metabolisms.

Just like the phototrophic bacteria can gain energy from sunlight. The chemotrophic bacteria can gain energy from the various chemical compounds.

Some bacteria can use inorganic compounds such as H₂S and NH₃; organic compounds such as Succinate, glucose, and amino acids as a source of electrons to derive energy.

Some bacteria can synthesize all of their food from inorganic substances like H₂O, CO₂, H₂S with or without the use of sunlight.

There are some bacteria that feed on the ready-made food from organic substances, either living or dead. Those that feed on the living organisms act as parasites and those that feed on the dead organisms act as decomposers.

There are some bacteria that feed by living in close association with other organisms as symbionts. The common examples are the nitrogen-fixing bacteria like Bacillus radicicola, etc.

How do chemosynthetic bacteria get energy?

Chemosynthetic bacteria are also termed as chemotrophs. They gain energy from chemical compounds to prepare their own food, and they cannot carry out photosynthesis.

Photosynthetic bacteria performs the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter to feed on, by using the source of sunlight as energy.

Unlike the Photosynthetic bacteria, Chemosynthetic bacteria perform the biological conversion of carbon-containing molecules like carbon dioxide or methane and various other nutrients into organic matter to feed on by using the source of energy released by inorganic chemical reactions as energy.

In simple words, chemosynthetic bacteria uses the energy derived from oxidation of inorganic compounds (like hydrogen gas, hydrogen sulfide) or ferrous ions or nitrates as a source of energy, rather than sunlight.

In chemosynthetic bacteria, it has been seen that different species use different pathways to get energy all by chemosynthesis.

In simple words, all chemosynthetic organisms use energy released by chemical reactions to make a sugar and amino acids, but different species use different pathways to do so.

For example, Nitrifying bacteria like Nitrosomonas, Nitrococcus, etc. that live in the soil use the source of carbon as carbon dioxide and obtain energy by oxidizing ammonia into nitrate.

Another example is the Sulphur bacteria like Thiobacillus denitrificans that can use the source of carbon as carbon dioxide and obtain energy by oxidizing H₂S.

How do autotrophic bacteria get energy?

Autotrophic bacteria are those bacteria that can prepare their own food to get energy. Both photosynthetic bacteria and chemosynthetic bacteria fall into the types of autotrophic bacteria.

Autotrophic bacteria synthesize all of their food from inorganic substances like H₂O, CO₂, H₂S with or without using the source of sunlight as energy to synthesize the food.

If autotrophic bacteria use sunlight as the source of energy to synthesize all their food from inorganic substances like H₂O, CO₂, H₂S then they are called Photosynthetic bacteria.

And, if autotrophic bacteria use the energy derived from oxidation of inorganic compounds like H₂, H₂S, or ferrous ions, or nitrates as the source of energy to synthesize all their food from inorganic substances like H₂O, CO₂, H₂S then they are called Chemosynthetic bacteria.

In the most simple words, the Photosynthetic bacteria use sunlight energy, and Chemosynthetic bacteria use chemical energy to synthesize their food from inorganic substances like H₂O, CO₂, H₂S.

See, the concept is that the bacteria will need to prepare its own food to get the energy for its survival. For preparing its own food it will act on the various inorganic substances like H₂O, CO₂, H₂S present in its surroundings by using external energy like chemical energy or sunlight energy to break down those above inorganic substances into sugar, amino acids, etc. for feeding and getting energy.

For example, Autotrophic bacteria like Chromatiiun. Theopedia rosea, Thiospirilium, etc. obtain food and energy from sulfur compounds like H₂S by using the energy of sunlight.

Another example is that the Autotrophic bacteria like those of the Sulphur bacteria that includes Thiobacillus, Beggiatoa, etc. obtain food and energy from sulfur compounds like H₂S by using the chemical energy released by oxidizing certain inorganic substances with the help of atmospheric oxygen.

How do heterotrophic bacteria get energy?

Heterotrophic bacteria are those types of bacteria that belong to the heterotrophs category. They are not able to make their own food to get energy like autotrophs, but they can feed on ready-made food like dead and living organisms.

The heterotrophic bacteria obtain their ready made food and energy from organic substances which are either living or dead.

In very simple words, you can also say that the heterotrophic bacteria can take the sugars they need to survive and reproduce from their environment, rather than making the sugars themselves from carbon and hydrogen compounds.

Heterotrophic bacteria are of the following types due to their different types of heterotrophic nutrition. They are: Photoheterotrophic bacteria, Saprophytic bacteria, Parasitic bacteria, and Symbiotic bacteria.

Photoheterotrophic bacteria need organic carbon, so they need the carbon produced by plants or other organisms in the form of carbohydrates, fatty acids, and alcohol for getting their nutrients.

Photoheterotrophs can also use sunlight energy to fulfilling some amount of energy requirement. As they depend solely on light energy to generate ATP through photophosphorylation.

Photoheterotrophic bacteria can utilize light energy but cannot use CO₂ as their sole source of carbon. They obtain energy from organic compounds to satisfy their carbon and electron requirements.

Examples of Photoheterotrophic bacteria are Purple non-sulfur bacteria like Rhodospirillum, Rhodomicrobium, Rhodopseudomonas palustris, etc.

Saprophytic bacteria obtain their food from the dead and organic decaying matter such as leaves, fruits, vegetables, meat, animal feces, leather, humus, etc. For example: Bacillus mycoides

Parasitic bacteria are those that can obtain their nutrition from the tissues of the hosts on which they grow. These bacteria can cause various diseases in both plants and animals.

Example of Parasitic bacteria includes Bacillus typhosus, Bacillus tuberculosis, etc.

There are some bacteria that feed by living in close association with other organisms as symbionts. These are also called Symbiotic bacteria.

The common examples of Symbiotic bacteria are the nitrogen-fixing bacteria like Bacillus azotobacter, Rhizobium spp.,Clostridium, etc.

How do aerobic bacteria get energy?

Aerobic bacteria are those bacteria that needs oxygen for their survival as they utilize oxygen for their growth and oxygen-based metabolism.

Aerobic bacteria can be of both Autotrophic (can prepare their own food) and Heterotrophic (cannot prepare their own food).

Aerobic bacteria, let be autotrophic or heterotrophic bacteria, will require oxygen to grow because their methods of energy production and respiration depend on the transfer of electrons to oxygen, which is the final electron acceptor in the electron transport reaction.

Not all aerobic bacteria are strictly aerobic, that is, some bacteria are Obligate aerobes meaning that they strictly require oxygen for aerobic respiration and can’t survive without oxygen.

Others are Facultative aerobes, that is, they can switch to anaerobic methods if oxygen is not present.

During cellular respiration, obligate aerobes use oxygen to oxidize substrates like carbohydrates and fats and generate energy.

On the other hand, Facultative aerobes use oxygen if it is available during cellular respiration, but also have anaerobic methods of energy production.

Examples of aerobic bacteria are Nocardia sp., Psuedomonas aeruginosa, Mycobacterium tuberculosis, Bacillus sp., etc.

How do anaerobic bacteria get energy?

Anaerobic bacteria are those bacteria that don’t need oxygen for their survival as they are capable of living in the absence of molecular oxygen.

Anaerobic bacteria can be of both Autotrophic (can prepare their own food) and Heterotrophic (cannot prepare their own food).

Anaerobic bacteria, let be autotrophic or heterotrophic bacteria, will not require oxygen to grow, sustain, and multiply.

Not all anaerobic bacteria are strictly anaerobic, that is, some bacteria are Obligate anaerobes meaning that they strictly do not require oxygen for anaerobic respiration and can only survive without oxygen.

Others are Facultative anaerobes, that is, they can switch to aerobic methods if oxygen is present.

They do not require oxygen because they can convert their organic food like carbohydrates, fats, etc. into simpler compounds to produce chemical energy (ATP) in their cell by using the electron transport chain system to pass the electrons to the final electron acceptor, which may be an inorganic or an organic compound, but not oxygen.

In simple words, in anaerobic respiration, glucose breaks down without oxygen. The chemical reaction transfers energy from glucose to the bacterial cell. Anaerobic respiration produces lactic acid, rather than carbon dioxide and water.

For example, Methanogens are Obligate anaerobic bacteria that produce ATP energy for their own cell from the biosynthesis of methane. They are only found in oxygen-free environments and participate actively in the carbon cycle.

It has been also seen that some Obligate anaerobes use fermentation, while others use anaerobic respiration.

Fermentation is the extraction of ATP energy from carbohydrates (like glucose) in the absence of oxygen through the action of various enzymes that the bacterial cell can produce. For example: Lactobacillus acidophilus is an anaerobic Lactic acid bacteria that can convert sugars to lactic acid by producing the enzyme called lactase.

Are bacteria animals or plants?

Bacteria are neither plants nor animals. They fall into their own Kingdom Monera, which is totally different from Kingdom Plantae that includes all plants, and Kingdom Animalia that includes all animals.

According to the 5 Kingdom Classification System: Animals belong to Kingdom Animalia, Plants belong to Kingdom Plantae, Fungi belong to Kingdom Fungi, Protists belong to Kingdom Protista, and Bacteria belong to Kingdom Monera.

Bacteria and are found in abundance in nature and they are unicellular and prokaryotic microscopic cells. Whereas, plants and animals are multicellular and eukaryotic organisms.

Because bacteria are prokaryotes and different from plants and animals. They do not have a nucleus and so no membrane-bound organelles.

Whereas, plants and animals cell do have a well-defined nucleus and various membrane bound organelles.

Although it’s clear that they are neither plants nor animals, but the recent findings indicate that bacteria are more like animals than plants in terms of biomass.

So, it will be just better to say that bacteria are unique organisms and deserve their own separate classification system. And, so bacteria are neither animals nor plants.

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