MONERA KINGDOM: CHARACTERISTICS, CLASSIFICATION AND EXAMPLES - BIOLOGY - 2025

The kingdom monera or monera is formed by bacteria, prokaryotic unicellular organisms that do not have a nuclear membrane or a specific form of nutrition. They can be autotrophs - they are capable of creating their own food - or heterotrophs - they obtain their food source from other organisms. The monera kingdom contains organisms with the simplest structures compared to the other kingdoms.

This kingdom groups all living beings that are unicellular (that have only one cell). It is considered the most primitive group in the world and is part of the five biological kingdoms. It is also known by the name of prokaryota or prokaryotae.

Prokaryotic cell

The word monera is derived from the Greek word moneres which means "unique." It refers to unicellular prokaryotes and they are the simplest and oldest life forms on planet Earth.

Bacteria are universal because they can be found almost anywhere, even in the most extreme conditions. They are found in the air you breathe and even in the stomachs of humans and other animals.

Most organisms in the monera kingdom can reproduce by the type of asexual reproduction called binary fission. In this process, the cell copies its DNA and then divides into two identical cells.

The monera kingdom is classified into two groups: Archaebacteria and Eubacteria.

In the Archaebacteria group there are microbes known as Extremophiles, capable of living in extreme conditions. They are divided into thermophiles, halophiles, and methanogens.

In the Eubacteria group are those considered as true bacteria; They have a cell wall and a flagellum that helps with movement.

The taxon monera was first proposed as a phylum by Copeland in 1866. In 1925 it was elevated to the rank of kingdom by Édouard Chatton.

History

In 1866 Ernst Haeckel proposed the taxon monera as a phylum. Over the years and after much research, in 1925 Édouard Chatton raised the edge to the rank of kingdom.

In 1969, the last commonly accepted megaclassification was made with the taxon monera. It is the five kingdoms classification system established by Robert Whittaker.

Later in 1977, Carl Woese together with his collaborators introduced the three-domain system based on: bacteria, archaea and eucarya.

Structure

They are characterized by having cells without a nucleus, without mitochondria, without a nuclear membrane and with a rigid cell wall that surrounds the plasma membrane.

Because they have no nucleus, all the genetic material in cells floats freely in the cytoplasm and the only parts of the cell that make it up are the cell wall and ribosomes.

Organisms of the monera kingdom contain DNA, which is included in the cytoplasm called the nucleoid. The cytoplasm is enclosed by a plasma membrane that is under the cell wall composed of lipids and proteins.

Main characteristics of the brunette kingdom

Its reproduction is asexual

The reproduction of these organisms is asexual and they multiply by excision or bipartition, during a short period. One bacterium can produce up to a million successors. The cell makes a duplicate of itself and a DNA molecule passes into a newly formed cell, these two cells being genetically identical.

Binary fission does not allow bacteria to acquire genetic diversity, which is necessary for bacteria to withstand changing environments.

Prokaryotic fission, binary fission, is a form of asexual reproduction.

Bacteria have the ability to mix genes through various processes. These processes include conjugation, transformation, and transduction.

Cilia and flagella

The organisms of the monera kingdom are mobilized by the presence of cilia or flagella, although some are almost immobile. Bacteria move in hair-like extensions known as flagella, which are longer than cilia but smaller in number.

Flagella in prokaryotes are much thinner than in eukaryotes and bind to the cell surface rather than to the cytoplasm.

They can be found on the front of the back of the bacteria, on both ends, or sometimes on its entire surface. Flagellum sweeps are a helix motion to help bacteria move.

Bacteria can also move around in slime secretion, and they glide along surfaces. However, other bacteria move by axial filaments. The axial filaments make the cell turn and move like a corkscrew.

They have means of defenses

Although it is not obvious, the organisms in the Monera kingdom do have some means of defense. In some species of bacteria, a capsule made of polysaccharides protects the bacteria from phagocytes (such as white blood cells) and from desiccation.

Certain bacteria also have means of movement that they can use to get away from things that can harm them.

They are resistant

When living conditions become too harsh to support bacteria, they can develop a tough protective wall around their DNA and a small fragment of cytoplasm.

This creates a highly resistant and latent structure called an endospore. The rest of the cell that remains can die.

Fortunately for the bacteria, the endospore can withstand years of freezing or drought. When the conditions become suitable for bacteria to become active again, the endospore becomes an active cell again.

Habitat

Made up of single-celled prokaryotic organisms, members of the monera kingdom can live individually or in groups, and can be found in all types of habitats, including aquatic, terrestrial, and the human body.

The organisms of the monera kingdom can withstand very cold and very high temperatures, so they can live almost anywhere. Some of these organisms live in the intestines and benefit the digestion process.

However, they constitute a health problem for members of the animal kingdom, since some organisms can cause dangerous and deadly diseases.

Size and shape

They can be round, corkscrew or corkscrew-shaped, and some have hairs for attachment or tail flagella.

They are the simplest prokaryotic cell structures and their size is small, generally measuring 1 micron.

Various types of breathing

Respiration in these organisms varies, they can be:

• Obligate aerobes: they must have oxygen to survive.
• Obligatory anaerobes: they cannot survive in the presence of oxygen.
• Facultative anaerobes: can survive with or without oxygen.

Some bacteria are autotrophic organisms, that is, they get carbon from carbon dioxide. In turn, the organisms that use light to obtain their energy are known as photoautotrophs.

Chemotrophs are bacteria that receive their energy from inorganic compounds such as hydrogen sulfide and use energy to run the activities of the cell.

The rest of the bacteria are heterotrophs, organisms that obtain carbon by ingesting organic molecules from decaying organisms or by living in another organism known as a host.

Prokaryotes lack organelles

With the exception of ribosomes, prokaryotes lack organelles. Prokaryotic cells are simple cells that do not have a membrane-bound nucleus or organelles. They have DNA and ribosomes.

They have no organelles, as the cytoplasm does the metabolic work, and technically only circular DNA is found in the nucleoid region and some ribosomes are found in a prokaryotic cytoplasm.

Enrich the soil

Bacteria also enrich the soil. For example, nitrogen fixers convert nitrogen in the air to nitrate, which plants need to live, and a number of cyanobacteria help fix nitrogen levels in the atmosphere.

These photosynthetic bacteria also contribute large amounts of oxygen to the atmosphere. Bacteria also break down matter and it is used for fertilizer.

They have special features

The DNA fragments are in the form of plasmids. Through these processes, bacteria can obtain new traits that they could not achieve only through binary fission.

These traits can include the ability to resist change in acidity, temperature and also have the ability to resist antibiotics.

Classification

The kingdom of monera is classified into bacteria -Archaebacteria and archaea -Eubacteria-.

Bacterium

Bacteria

Bacteria are the most abundant organisms on the planet and comprise all prokaryotic microorganisms, which do not have a defined nucleus. They are of different sizes and shapes, the same species can adopt different morphological types.

Depending on the species, they can measure between 0.5 and 5 μm, and some reach 0.5 mm. The smallest bacteria, belonging to the genus mycoplasma, measure only 0.3 μm.

In natural environments, bacteria can anchor to certain surfaces to form a cellular aggregate in the form of a layer called a biofilm or biofilm, which can congregate various bacterial species.

Bacteria can survive in more extreme environments, such as hot and acidic springs, in radioactive waste, in the deep sea and in terrestrial habitats.

Bacteria can also survive in humans and are found on the skin and in the digestive tract. It is estimated that there are approximately ten times more bacterial cells than human cells.

These bacterial cells can be harmless or beneficial. However, some bacteria can cause respiratory and infectious diseases, including cholera, diphtheria, scarlet fever, leprosy, syphilis, and typhus, among others.

Archaea

Archaea

Archaea are microorganisms that define the limits of life on Earth.

They are unicellular lacking a nucleus and are microscopic. Their cells are wrapped in various materials that give them high resistance to antibiotics.

Although they are very similar to bacteria, they are very different and have very particular characteristics. Due to this, they have great biotechnological potential.

They live in the most extreme environments on the planet. They can be achieved in environments such as hydrothermal vents and hot springs.

They are capable of growing in an environment of high and low temperatures; they survive at high salt concentrations or low pH, where the survival of any other living being is impossible.

They can be found near crevices deep in the sea at temperatures above 100 ° C, in hot springs, or in extremely alkaline or acidic waters. They survive in the digestive tracts of cows, termites, and marine life where methane is produced.

Archaea feed on inorganic compounds, among which are hydrogen, carbon dioxide, alcohols, sulfur, and iron.

They are used for the production of bioplastics, which degrade quickly and do not pollute. In science they are used as a model for the search for life outside planet Earth.

Nutrition

Nutrition in the Monera kingdom is usually very diverse. However, it can be said that they have basically two types of nutrition: autotrophic and heterotrophic.

Autotrophic nutrition

Autotrophic prokaryotes are those that produce their own food. Autotrophic nutrition is divided into chemosynthetic and photosynthetic.

Chemosynthetic nutrition is one in which bacteria generate their food based on inorganic chemicals as a source of energy.

Chemosynthetics is the method used by all those bacteria that are found in places where sunlight does not reach.

For its part, photosynthetic nutrition is used by bacteria, plants and algae that use sunlight to transform inorganic matter into organic matter for their development.

Heterotrophic nutrition

It is the way organisms get their food from other organisms.

Heterotrophic nutrition has organic carbon as its source of nutrition. There are three types of heterotrophic nutrition in bacteria:

• Saprophytic nutrition: is one in which bacteria feed on decomposing organisms.
• Parasitic nutrition: in this type of nutrition, bacteria feed on living organisms.
• Symbiotic nutrition: organic matter is obtained from another living being, where both benefit.

Examples

Some examples of organisms of the Monera kingdom are:

Koch bacillus

It is the bacterium that causes tuberculosis.

Chlamydia

Gram negative bacteria, causing sexually transmitted diseases.

Escherichia cabbage

Known as E. coli, it is a Gram-negative rod of the Enterobacteriaceae family that causes gastrointestinal infections.

Salmonella

It is an anaerobic bacteria that contaminates food and causes intestinal disorders in humans.

Clostridium septicum

It is a Gram positive anaerobic bacterium. It is part of the intestinal flora of humans and is the cause of abscesses, grangrene, neutropenic enterocolitis and sepsis.

Vibrio

It is a genus of bacteria included in the gamma group of proteobacteria. They cause diseases in the digestive tract and are the cause of cholera.

Neisseria gonorrhoeae

It is a Gram negative diplococcus that causes gonorrhea, which is a sexually transmitted disease.

Helicobacter pylori

It is a Gram negative bacteria. It only survives in the digestive system of humans.

In some cases, the presence of H. pylori is unknown since there are no symptoms. However, in other cases it can cause gastritis and ulcers, among other conditions.

Staphylococcus

They are microorganisms that are present in the mucosa and on the skin of humans and other mammals and birds. Staphylococcus can cause diarrhea, vomiting, and nausea.

Bifidobacterium

It is Gram-positive, anaerobic, and non-motile. They are a group of bacteria that settle in the intestines. Bifidobacteria can be used to restore the intestinal flora.

Streptococcus

It is a bacterium formed by Gram positive cocci. Streptococcus is made up of two groups.

Group A streptococcus cause infection in the throat, on the skin, among others. Group B streptococci are the pathogens that cause blood infections, pneumonia, and meningitis in newborns .

Serpulina hyodysenteriae

It is a bacterium that causes swine dysentery, which only affects pigs.

Sorangium cellulosum

It is a Gram-negative bacterium and has the largest known genome in a bacterium.

Positive aspects of the monera kingdom

The monera kingdom includes bacteria that can be found in animals, humans, and plants. These can be beneficial, since they kill organisms that cause pathogenic diseases.

Another positive aspect includes its participation in the production of antibiotics, such as streptomycin, which is used to treat infections.

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