Monera Kingdom

What is the Monera Kingdom?

The Monera kingdom is the name of a classification of living beings that grouped single-celled prokaryotic organisms and was composed mainly of bacteria and archaea, the most abundant life forms on the planet.

Prokaryotic organisms are composed of a single cell without a defined nucleus. In fact, the word monera comes from the Greek moneres, which refers to the “simple” and “solitary”. Hence it was used to describe the organisms of this kingdom.

At the moment, The Monera kingdom is not considered one of the seven kingdoms of nature. These organisms are now classified into two different kingdoms: archaea (kingdom Archaea) and bacteria (kingdom Bacterium).

But why was Monera considered a separate kingdom for so long? In 1866, the German naturalist Ernst Haeckel had divided living beings into three large groups: Animals, Plantae and Protist.

The organisms of the kingdom Monera were part of the kingdom Protista in one of its subdivisions, which also included organisms with eukaryotic cells.

But later, in 1920, the French biologist Édouard Chatton discovered the existence of cells without a defined nucleus and established two groups of cells that he named eukaryotes and prokaryotes.

Later, Hebert Copeland, an American biologist, proposed in 1938 the creation of the kingdom Monera, in which prokaryotic organisms were found.

However, in the 1970s, the American microbiologist Carl Woese noticed that within the Monera kingdom there were two different groups: bacteria and archaea, giving rise to the creation of two new kingdoms, with which Monera ceased to exist. be considered a kingdom in itself.

Characteristics of the Monera kingdom

Bacterium Escherichia colicausing gastrointestinal infections.

Among the general characteristics that differentiate the organisms that belong to the Monera kingdom, the following can be named:

They are prokaryotic cells: that is, they lack a cell nucleus.
They are the smallest cellular organisms that have been found, between 0.2 and 3 microns in diameter.
Your respiration can be aerobic or anaerobicthat is, some of the bacteria in this kingdom need oxygen to exist and others do not.
They can live individually or in bacteria that form colonies.
They can move autonomouslythanks to the cilia and flagella that some of these organisms have.
Its habitat is variedcan be found both on land and in water, on and within other living beings.
They reproduce asexuallyby splitting or bipartition.
Nutrition is usually heterotrophicThey depend on other organisms to obtain their sustenance. In some cases it is autotrophic when they can synthesize their own nutrients.
The morphology is variedsome are round, cane or corkscrew shaped.

Classification of the Monera kingdom

The classification of bacteria has been modified over the years thanks to new findings made by scientists. In principle there were two classifications, bacteria and cyanobacteria.

Then the classification proposed by Woese was used, which was made up of four divisions:


They are unicellular prokaryotic microorganisms. Its name was due to its similarity to bacteria, although today it is known that they are different organisms and even have their own kingdom (Archaea).

Some examples of archaebacteria are methanogenic archaea, crenarchaeota, and halobacteria.

Gram positive

They are prokaryotic microorganisms with a cell wall rich in peptodoglycan, a mesh of amino acids and sugars that protects the cell membrane of the bacteria.

Examples of this type of microorganisms are lactobacilli, micrococci, staphylococci and actinobacteria.

Gram negative

They are bacteria whose cell wall is poor in peptidoglycan but rich in lipids.

Meningococci, chlamydia, and intestinal bacteria such as Escherichia coliare some examples.


They are bacteria that do not have a cell wall, very difficult to detect under the microscope due to their almost imperceptible size. Some of them are pathogenic parasites of vertebrates, including humans.

Examples of mycoplasmas are anaeroplasmatales, entomoplasmatales, mycoplasmatales and Mycoplasma pneumoniaewhich can cause pneumonia in humans.

Examples from the Monera kingdom

Clostridium botulinumthe bacteria that causes botulism.

Below are some examples of the organisms that were considered part of the kingdom Monera, which are largely bacteria.

chlamydia trachomatis: Gram negative bacteria that cause sexually transmitted infections.
Vibrio vulnificus: It is a Gram-negative bacteria that causes infections in humans.
Bifidobacteria: bacteria found in the colon and involved in digestion.
Escherichia coli: bacteria that causes gastrointestinal infections.
Lactobacillus casei: It is a Gram positive bacteria, it produces lactic acid and is found in the intestines and mouth of humans.
Clostridium botulinum: It is a bacillus found in the soil and that generates the toxin that causes botulism.

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