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Kingdom Monera – Definition, Classification, Characteristics, Examples

Last Updated : 08 Apr, 2024
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Kingdom Monera is a group of prokaryotic organisms that are unicellular and lack a nucleus. They are the oldest organisms on Earth and all living things developed from them. Kingdom Monera includes two main groups – Archaebacteria and Eubacteria. They live in extreme conditions of the environment such as high temperatures, high salt concentrations, hot springs, deep oceans, and salt marshes.

Monera are either autotrophs or heterotrophs. They are also found in moist environments such as snow, and deep oceans, and as parasites in other organisms. In this article, you can find the Kingdom Monera notes.

Kingdom Monera

Kingdom Monera was first proposed as a phylum by Ernst Haeckel in 1866, however in 1925 Edouard Chatton promoted the phylum Monera into the kingdom Monera. The kingdom Monera is the only kingdom in the whole classification system that consists of all the prokaryotes. However, the kingdom of Monera has been broken into primitive prokaryotes i.e. the archaebacteria, and modern prokaryotes i.e. the eubacteria.

Only the prokaryotes are members of the Kingdom Monera. They are single-celled organisms that are typically found in damp environments. They lack true nucleus in any of the species that make up this kingdom instead they have a region containing their genetic material called the nucleoid. They usually have circular DNA. Cell organelles that are bound to membranes are absent in monerans. They can be discovered as parasites in other creatures or free-living organisms in hot springs, deep oceans, and snow.

A labeled diagram of Kingdom Monera is shown below:

Bacterial Cell

Typical Prokaryotic Cell

Characteristics of Kingdom Monera

Following are some of the characteristics of the kingdom Monera;

  • The monerans are single-celled organisms.
  • They have 70S ribosomes in them.
  • The nuclear membrane does not enclose the DNA, which is exposed in the form of a nucleoid.
  • Monera is devoid of cellular organelles like lysosomes, plastids, centrioles, Golgi bodies, mitochondria, and so on.
  • With the help of binary fission or budding, they reproduce asexually.
  • Peptidoglycan layers make up the cell wall of prokaryotes.
  • They have a locomotory organ called the flagellum.
  • They exhibit many feeding strategies like; autotrophic, parasitic, heterotrophic, and saprophytic.

Classification of Kingdom Monera

The kingdom Monera is classified based on their appearance on the planet Earth into primitive archaebacteria, and modern eubacteria. However, there is a third group called Cyanobacteria.

Ribosomal ribonucleic acid (rRNA) investigations of the genetic makeup of the organisms led to the split of prokaryotic organisms into the Bacteria and Archaea domains. Additionally, they are useful in the synthesis of various foods and antibiotics.


Some of the characteristics of the group archaebacteria are;

  • They are the oldest bacteria
  • They can be found in extreme environments such as methane marshes (methanogens), hot springs (thermophiles), and highly salty places (halophiles).
  • Since their cell walls are built differently than those of other bacteria, they can endure extreme environments.
  • Autotrophic mode of feeding is the method of life as they are the first living organisms on earth.
  • Unique nucleotide sequences make up its tRNA and rRNA.
  • “True bacteria” is another name for eubacteria.
  • It moves with the aid of flagella.
  • A few bacteria have small extensions called pili on their cell surfaces that aid them in a form of sexual reproduction called transduction. The pathogen can connect to a host with the aid of pili as well.
  • Methanogens are crucial in the sewage treatment process. Archaebacteria are a major source of food for numerous creatures.
  • Some of the examples are; Methanobacterium, Halobacterium, etc.


Some of the characteristics of the eubacterium are;

  • The name “eubacterium” also known as “eubacteria” is used to identify and separate the archaebacteria from a group of modern prokaryotic bacteria. The term “bacteria” now refers to modern bacteria.
  • They have a cell wall that is mainly made of peptidoglycan layers.
  • Found in normal conditions all over the surrounding environment.
  • They can be both aerobic and anaerobic conditions.
  • Depending on the composition of the cell wall and the dye they absorb, they are categorized as either gram-positive bacteria or gram-negative bacteria.
  • They are environmental decomposers, parasites, and even free-living.
  • Some of the examples are; Rhizobium, Pseudomonas, etc.

Also Read: Difference Between Gram-Positive and Gram-Negative Bacteria

Cyanobacteria (Subgroup)

Some of the common characteristics of cyanobacteria are;

  • Also called blue-green algae.
  • These microbes are naturally photosynthetic.
  • They contain phycobilins, carotenoids, and chlorophyll pigments that aid in the process of photosynthesis.
  • They inhabit an aquatic environment only.
  • Some of these even fix nitrogen in the air.
  • Some of the examples of cyanobacteria include Nostoc, Anabaena, Spirulina, etc.


Tiny, solitary microscopic organisms are known as bacteria. Nearly all areas of the world are home to bacteria, which are essential to their ecosystems. Some species can tolerate environments with high pressure and temperatures. Animal bodies also contain bacterial species and the majority of them are beneficial and not harmful.

Bacteria are divided on the basis of their shapes:

  • Spheres (coccus),
  • Rods (bacillus),
  • Comma-shaped (vibrio), and
  • Spirals (spirochaetes).

Bacteria can cause diseases but they are useful too our gut contains bacterial species that aid in digestion, also bacteria are crucial to biotechnology for commercial purposes.

General Structure of Bacteria

The prokaryotic cells have more or less the below mentioned structures and appendages common to all groups;


Many strains of bacteria contain a tertiary, polysaccharide-based (complex carbohydrates) capsule as a form of protection. The most crucial function of capsules is to prevent the bacteria from drying up and from being phagocytosed (engulfed) by larger organisms or digestive juices. The bacterial species like E.coli and Streptococcus pneumonia, the capsule is a significant virulence component that gives them their ability to infect.

Cell Envelope

Inside the cell wall and in some strains of bacteria an outer capsule make up the 2 to 3 sections that make up the cell envelope.

Cell wall

Every bacterium is surrounded by a thick cell wall made of the polysaccharide macromolecular peptidoglycan. The cytoplasmic membrane is encircled by the cell wall, which also gives the cell shape and shields it from the external environment. Additionally, it acts as the base for protruding extensions like the flagella and pili that emerge from the cytoplasmic barrier and extend outside the cell wall.


The processes for cell development, metabolism, and replication take place in the cytoplasm, or protoplasm, of microbial species. Water, enzymes, nutrients, waste products, and gases make up its gel-like matrix, which also houses ribosomes, chromosomes, and plasmids, among other cell components. The organelle are enclosed within the cell envelope.


These are some unique very small, extrachromosomal DNA that is found in some species of bacteria. It has been demonstrated that plasmids play a key role in the transfer of traits with specific characteristics, such as resistance to antibiotics, heavy metal resistance, and virulence factors required for the disease of plants or animal hosts.

Plasmids are incredibly helpful tools in the sciences of molecular genetics, particularly in the field of genetic modification, due to their ability to incorporate individual genes within them and being non-essential genetic material.

Plasma Membrane

The plasma/cytoplasmic membrane, a barrier of lipids and proteins, covers the inside of the bacterium and controls the movement of substances into and out of the cell. All live cells have this characteristic structure, which gives them the ability to actively engage with their surroundings. They are dynamic and ever-changing adjust to various environmental factors and also keep the cellular components packed.


For microorganisms that possess them, flagella (plural, flagellum) are hair-like structures that enable them to move with the help of beating like a turbine manner. A bacteria can have them across its surface or at one or both of its ends that assist the bacterium in moving toward nutrients, away from harmful substances, or in the instance of the symbiotic cyanobacteria, toward the light, etc.


The chromosomal DNA is found in a cytoplasmic area known as the nucleoid which is not membrane-bound. Sometimes it may consist of more than one smaller circular DNA.


Numerous bacterial species feature pili (plural: pilus), which resemble tiny hairs that protrude from the surface of the cell. These protrusions let the bacteria connect to various tissues and surfaces like; teeth, bowels, and rocks. For conjugation, two bacteria exchange plasmid DNA pieces through specialized pili.


These are made of RNA that helps in the conversion of genetic information into functional proteins; the biomolecules that carry out all of the tasks required by cells. Eukaryotic ribosomes and bacterial ribosomes are similar in function, however, bacterial ribosomes are smaller and have a marginally different molecular makeup.

Conclusion – Kingdom Monera

In conclusion, Kingdom Monera consists of archaebacteria and eubacteria. It represents the earliest forms of life on Earth, thriving in extreme environments and serving as essential components of various ecosystems. While lacking a true nucleus, these prokaryotic organisms exhibit diverse feeding strategies and play vital roles in nutrient cycling. Despite being unicellular, Monera display remarkable adaptability and are crucial in fields including biotechnology to environmental science.

Also Read: Five Kingdom Classification: Features, Examples

FAQs on Kingdom Monera

Define Kingdom Monera.

Kingdom Monera includes all the prokaryotic organisms that are present in the Earth. They lacks a true nucleus and membrane bound organelles. They consists of the oldest organism that inhabited the planet.

Give Five Examples from Kingdom Monera.

Five most common examples from kingdom Monera are; Streptococcus, Bacillus, Cyanobacteria, E.coli, Pseudomonas, etc.

Give Four Basic Characteristics of the the Kingdom Monera.

Four basic characteristics of kingdom Monera are – unicellular, lack a well-defined nucleus and membrane bound cell organelles, and presence of 70S ribosomes.

What are the Two Main Groups of the the Kingdom Monera?

The two main groups of kingdom Monera are; Archaebacteria, and Eubacteria.

Name Some Common Places Where Members of the Kingdom Monera are Found?

Members of kingdom Monera are ubiquitous in nature i.e. they are found everywhere like soil, water, air, human gut, skin, hydrothermal vents, deep oceans, etc.

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