What Kinds Of Bacteria Are Decomposers?

Bacteria possess many functions and characteristics that have been thoroughly researched over recent decades.

While naked to the human eye, they are present both inside and outside of most organisms as well as being on surfaces and substances like water, food and soil.

What Kinds Of Bacteria Are Decomposers?

While it is well known that bacteria often feed on living organisms with some even producing their own food, it can sometimes be far less clear if they count as decomposers which refers to organisms that feed on dead and decaying organism matter of plants and animals, in turn breaking them down even more. 

Decomposers play a vital role in preventing different types of organic materials from piling up in the environment and as so they contribute greatly to the ecosystem.

Here are all the key facts on what kinds of bacteria are classed as decomposers and if so, how exactly it works.

Are Bacteria Classed As Decomposers?

Not only are most kinds of bacteria classed as decomposers, but they are actually incredibly important to the process.

Most bacteria found in soil and compost are decomposers and can break down just about any type of organic matter. They are vital in the recycling of nutrients and are often involved in the early stages of decomposition. 

Colonies of bacteria will begin the process of decomposition shortly after the death of an organic life form, whether this is a plant, animal or human. 

Bacteria therefore can very easily break down dead organic material into simpler chemical nutrients including carbon and nitrogen compounds and are considered the most abundant decomposers on Earth considering how varied and easily spread bacteria is.

Here are just a few of the reasons bacteria are considered the greatest decomposers:

  1. They are ubiquitous and are found essentially everywhere from soil to radioactive waste 
  2. They are both symbiotic and parasitic 
  3. They are incredibly small often 0.5 – 5.0 micrometers in length 
  4. They have less generation time 
  5. They multiply at a rapid rate through asexual reproduction 
  6. Bacteria is comfortable surviving in most environmental conditions and have developed an immunity to harsher climates 

What Does Bacteria Decompose?

Because of how widespread groups of bacteria are and how they are adjusted to just about every kind of environment, the actual materials they decompose are incredibly varied. 

Dead organisms including animals, food and humans are common in the decomposition process, however more specific options include decomposing lignin and pectin found in dead leaves, as well as breaking down polysaccharide complexes in plants and proteins and lipids in the body of humans and animals. 

They can therefore begin the process in any environment whether it be near the top of the soil, underwater or even within a body. 

How Does Bacteria Decompose?

The process of bacteria decomposing material is commonly referred to as bacterial digestion, and works by the bacteria absorbing food and then releasing enzymes into the environment around them. 

The enzymes then break down organic matter into simple compounds, such as glucose and amino acids, which is then absorbed by the bacteria. 

This process may seem vital to the life of the bacteria, but it is actually incredibly crucial and beneficial for the ecosystem in general.

While decomposers break down dead plants and animals, they also break down most other materials gone to waste which can build up. 

If decomposers such as bacteria weren’t in the ecosystem, then not only would plants not get their essential nutrients, but dead matter and waste would also build up much faster.

Additionally, if bacteria were to suddenly stop decomposing altogether, the carbon would remain locked in dead organisms and could only be released through a process of combustion. 

What Types Of Bacteria Are Decomposers?

While most bacteria will begin the decomposing process as soon as a living organism dies or begins to decay, there are some more suited to forms of decomposition than others with some bacteria that feed on live organisms and consumers not being classed as decomposers at all. 

Here are some of the most common bacteria variants involved in the decomposition process:



Also commonly known as the ‘Purple bacteria’, Proteobacteria make up one of the largest phyla and most versatile phyla in the bacteria domain.

The name actually comes from the ancient Greek God Proteus known to assume different shapes, which makes sense since they contain several types of smaller bacteria including phototrophs and heterotrophs with many taking on different appearances. 

There are over 460 types of Proteobacteria known to date all recognised as common decomposers.



In terms of bacteria decomposers, Actinobacteria are known as one of the largest possessing the best diversification of organisms.

These bacteria work primarily within the soil.

They look a lot like gray spider webs and are very important in decomposing organic matter in soil specifically because they are capable of breaking down complex plant compounds including chitin and cellulose.

Streptomyces is one variant of this bacteria that is very prevalent in the soil and actually looks more like fungi than bacteria, however they still decompose in the same way and are important for keeping the ground clean and free of built up waste.


Acidobacteria is a phylum composed of a huge variety of bacteria that are widely distributed and according to studies, their type is one of the most abundant groups on Earth.

In fact, it has been estimated that around 52% of total bacteria in the soil and about 20% of all microorganisms in the soil are a form of Acidobacteria.

So far, researchers have been able to identify 26 different subdivisions of the phylum acidobacteria which have now been placed into their own subdivisions to make recognising them easier.

Because of how widespread Acidobacteria are in the soil, they play an incredibly important role in the carbon cycle, especially for their role in degrading cellulose and lignin. 



Bacteroidetes are also a group of bacteria decomposers, however they work in slightly different areas.

They are a gram-negative bacteria found in all ecosystems and are particularly dominant in soil, but also in the gut of humans and animals.

Within the gut they work to degrade carbohydrates, carbohydrate based substances and proteins.

They are crucially important in the breakdown and release of energy from various organic molecules, and can also act as pathogens releasing toxic products during metabolism. 

They often form colonies between 1 to 3 mm in diameter and these can appear white or gray in color often characterized by a smooth and convex surface. 

Carbohydrates are the primary source of nutrition for Bacteroidetes and they break these down through a process known as fermentation which is very beneficial for the host as some of the energy produced is used by the host’s cells. 



A very large and diverse group made up of an estimated 250 genera, the majority of bacteria classed as Gammaproteobacteria are commonly found in terrestrial and aquatic ecosystems.

They are vital in the treatment of wastewater and as a source of energy. 

They are not only present in aquatic conditions however, these types of bacteria can also appear in the upper levels of soil such as with Bacillus Subtilis which is just one of the many decomposers. 

Other Forms Of Decomposing Bacteria

These bacteria groups mentioned above are the most common and most well studied decomposition variants known today, however there are a few other specific forms of bacteria that are known to decompose specific materials.

Thermobifida, Cellulosimicrobium And Cellulomonas 

These bacteria are soil based and are primarily concerned with breaking down cellulose into smaller sugars and producing exocellulase and xylanase.

The xylanase itself that these bacteria produce is used to break down hemicellulose by degrading linear polysaccharide xylan.

Streptomyces And Acidothermus 

These bacteria are known to break down cellulose by cleaving the inner bonds within the structure, and they do this through producing endocellulase.

Xanthomonas Oryzae 

These bacteria produce a variety of enzymes to help in decomposition including cellulases, esterases, and xylanases.

While these enzymes have been known to assist in the breakdown of cellulose and hemicellulose, they have also been linked with the breakdown of pectin commonly found in plants. 

How Do Bacteria Decomposers Gain Energy?

A singular decomposer will be able to retain its energy through a process called cellular respiration.

This involves using oxygen to convert glucose and other simple sugars including amino acids into a form of energy which can allow the cells to function and grow. 

The actual nutrients they use for the respiration process comes directly from the organic matter they decompose.

Not all decomposing bacteria will work this way however since it only works when oxygen is around.

Some bacteria will get their energy from a slightly different process known as ‘fermentation’ that is a common term used in beer and wine making.

It essentially means extracting energy from the sugars present in things like fruit without a need for oxygen that allows them to still decompose the material. 

For bacteria living in the ocean called chemosynthetic bacteria, they can work without oxygen completely and rely on other molecules instead if they are a decomposer.

If they are not involved in the decomposing process, then they can even survive underwater without organic material entirely. 

Fungi As Decomposers

Fungi is often very comparable to bacteria since it decomposes in much the same way.

Most fungi are decomposers called saprotrophs, they often feed on decaying organic matter and work to return nutrients to the soil for plants to make use of.

One of the many reasons fungi are considered so important as decomposers is because they are the only decomposers capable of breaking down wood and cellulose in plant wall cells, which makes them the primary decomposers in forests. 

Similar to bacteria that decompose, fungi also obtain their required nutrients from dead and decaying matter which then results in the further breakdown of these materials.

Majority of fungi are dependent on dead organic matter in their surroundings for nutrients, however they can also obtain nutrients from living plants and trees. 

They do this by secreting enzymes out of the tips of their hyphae, rather than actually engulfing food like an amoeba or ingesting and then digesting like an animal would.

Breaking down dead matter is actually the primary activity for most fungi and while a lot of what we see regarding them is very bad, the majority of fungi are just minding their own business and decomposing organic matter without killing anything. 

Here are just a handful of the several different enzymes produced by fungi and what organic material they are used to degrade:

  • Pectin – Pectin is known to be very diverse in structure so it can often take quite a variety of enzymes to be able to break it down, some of these enzymes include Pectate Lyase, Endoarabinanase and Alpha Rhamnosidase 
  • Galactomannan – Commonly found in the cell walls of fungi, these are used to break down Mannosidase, Galactosidase and Endomannanse. 
  • Xylan – The enzymes fungi will produce to break down Xylan include Xylosidase and Endoxylanase.

Because of how fungi is produced and how widespread they are on essentially every surface you can think of, they are often considered the best decomposer next to bacteria.

Not only are fungi responsible for turning organic matter into soil again, but the vast majority of the world’s plant families have some sort of symbiotic relationship with fungi in which the fungi will pass water and nutrients onto the roots of the plants and in turn the plants make sugars for the fungi to consume. 

Animals As Decomposers 

This refers mostly to animals who are also classed as decomposers that survive by feeding on the organic matter of dead plants and animals and are commonly referred to as detritivores.

Worms are the most common decomposers in this category, they feed on dead plants and animals directly rather than using enzymes to break them down the same way that bacteria and fungi do. 

Maggots and larvae are another common decomposer, since maggots will often start feeding on whatever organic material their eggs happen to be laid upon.

The mother will often lay the eggs on top of or inside the dead or rotting matter which the larvae will then use as a food source once the eggs have hatched.

They will feed on the food for about 5 days before they then find a dark and dry location to develop into their pupal phase. 

Maggots however do not have a developed digestive system that can work to physically break down dead organic material the way a worm can, therefore in a sense they function closer to bacteria and fungi since they instead use a variety of enzymes to break down organisms and use the obtained materials to grow. 

Termites are another decomposer known for breaking down decaying deadwood. Within a termite stomach there is a protozoa which can work to break down cellulose into digestible sugar.

Within these protozoans actually live bacteria that work within the metabolic process. 

Other animals that can be classed as decomposers include crabs that have been known to feed on dead plants and animals, as well as ants which also help in the breaking down of dead organic matter.

Sometimes however these types of animals are not referred to as decomposers because their process works a bit differently which can make them more commonly referred to as ‘scavengers’. 


While not all bacteria can be considered crucial in the decomposing process, there are some groups and variants that are very important to breaking down dead matter and largely contributing to the ecosystem in ways that we as humans cannot.

It’s important to note that bacteria is not the only organism involved in this process as they are assisted by fungi and certain types of animals who also work to prevent build up in their own unique ways and keep the Earth and plants healthy. 

Jennifer Dawkins

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