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Kingdom Monera – Definition, Classification, Characteristics, Examples

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The process of separating distinct classes depending on their features is known as biological categorization. This chapter requires both comprehension and memorization skills because there are many crucial terms and details that you must retain. The scientific process of grouping organisms into groups and subgroups based on their similarities and differences and arranging the unit in a hierarchy of classes is known as biological categorization.

Significance of classification

  • No organism can be studied in detail. The study of one or two organisms from a group is sufficient to reveal the key characteristics of the group.
  • It aids in the discovery of novel organisms.
  • Understanding the relationships between various groupings of organisms is aided by classification.
  • Without an appropriate classification scheme, it is impossible to study the organism of the past


  • Prokaryotes are members of the Kingdom Monera family. 
  • There is no real nucleus in any of the species that make up this kingdom. 
  • These are the planet’s oldest known microbes. 
  • Their nucleus does not contain their DNA. 
  • They are single-celled creatures that are typically found in damp environments. 
  • They can be discovered as parasites in other creatures, hot springs, deep oceans, and snow. 
  • Organelles that are bound to membranes are absent in monerans.
Bacterial Cell



  • The monerans are single-celled creatures.
  • They have 70S ribosomes in them.
  • A nuclear membrane does not enclose the DNA, which is exposed.
  • It is devoid of organelles like lysosomes, plastids, centrioles, bodies of Golgi, mitochondria, and so on.
  • By binary fission or budding, they reproduce asexually.
  • Peptidoglycan makes up the stiff cell wall.
  • The locomotory organ is the flagellum.
  • Environmental decomposers are those.
  • They exhibit many feeding strategies, including autotrophic, parasitic, heterotrophic, and saprophytic.

Classification of Monera


  • The name “eubacterium,” sometimes known as “eubacteria,” was once used to identify and separate the archaebacteria from a group of prokaryotic genuine bacteria. The term “bacteria” now refers to actual bacteria.
  •  Archaea (previously the Archaebacteria) and Eukarya, the other two domains of life, are genetically and physically separate from bacteria (the eukaryotes). 
  • 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. Early in Earth’s history, bacteria and archaea are assumed to have diverged from a common ancestor. 
  • Important differences between bacteria and archaea include the number of ribosomal proteins and the size and form of the ribosomal S unit.


  • These are the oldest bacteria and can be found in the harshest environments, such as marshes, hot springs, and salty places (halophiles) (methanogens).
  • Since their cell walls are built differently than those of other bacteria, they can endure harsh environments.
  • Autotrophic feeding is the method of life.
  • Unique nucleotide sequences make up its tRNA and rRNA.
  • True bacteria” is another name for eubacteria.
  • Peptidoglycans make up the stiff cell wall.
  • With the aid of flagella, it moves.
  • A few bacteria have small extensions called pili on their cell surfaces that aid them in sexual reproduction. A pathogen can connect to a host with the aid of pili as well.
  • Depending on the makeup of the cell wall and the stain they absorb, they are categorized as either gram-positive or gram-negative.
  • Eubacteria Rhizobium and Clostridium are two.


  • Additionally called blue-green algae, these include.
  • These microbes are naturally photosynthetic.
  • They contain phycobilins, carotenoids, and chlorophyll.
  • They inhabit a watery environment.
  • Some of these even fix nitrogen in the air.
  • Some cyanobacteria include Nostoc, Anabaena, and Spirulina.

Monerans are extremely helpful creatures. They contribute to the nitrogen cycle and improve soil quality. Additionally, they are useful in the synthesis of various foods and antibiotics. Methanogens are crucial in the sewage treatment process. Archaebacteria are a major source of food for numerous creatures.


Tiny, solitary organisms called bacteria exist. 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. In fact, it’s thought that there are more microbial components of the human body than there are human cells. The majority of microorganisms in the body are beneficial and even nontoxic. Infection is characterized by a comparatively small range of organisms. Microorganisms called bacteria to occur in a variety of forms. They may take the form of spheres, rods, or spirals. There are infectious, or harmful, bacteria that cause illness, but there are also beneficial bacteria. As an illustration, our digestive tract and gut contain bacteria that are crucial to our bodies’ ability to operate normally. The intriguing thing about microbes is that they make up a whopping 10 times as many cells in our body as human cells do. Additionally, bacteria are crucial to biotechnology. These are crucial in that they will once more assist the body in maintaining a healthy state.



Many strains of bacteria contain a tertiary, polysaccharide-based capsule as a form of protection (complex carbohydrates). The most crucial functions of capsules are to prevent the bacteria from drying up and from being phagocytosed (engulfed) by bigger microbes. In the main illness bacteria, like E.coli and Streptococcus pneumonia, the capsule is a significant virulence component. These organisms’ nonencapsulated mutations are not pathogenic, or avirulent.

Cell envelope

The inside cytoplasm membranes, 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 nutrient (polysaccharide) macromolecular peptidoglycan. The cytoplasmic membrane is encircled by the cell wall, which also gives the cell shape and shields it from the outside world. Additionally, it aids in securing protruding extensions like the flagella and pili that emerge from the cytoplasmic barrier and extend outside the cell wall.

Among the most crucial elements in the study and separation of bacterial species is the makeup of the bacterial cell, which differs greatly among bacteria. For instance, a moderately thick, mesh-like structure that enables the distinction between two fundamental types of bacteria Hans Christian Gram, a Danish physician, developed a method in 1884 that employs staining and washing to differentiate between the two kinds. Gram-positive are allowed to hold the purple hue of a gram stain after exposure because the design of their cell membranes retains the dye. When gram-negative bacteria are cleaned with an alcoholic or acetic solution, their thin cell walls easily release the dye.


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 and all of its elements are enclosed within the cell envelope. Microbes do not even have a nucleus that is surrounded by a cell wall like eukaryotic (true) cells do. The nucleoid is a part of the cell where the chromosome, a continuous line strand of DNA, is localized but not confined. The cytoplasmic is filled with all the other parts of the cell.

There are two ways that plasmids spread from one bacterium to another. During binary fission, copies of the majority of plasmid types located in the cytoplasm are transferred to daughter cells. When bacteria conjugate, or exchange genetic material, other forms of plasmids, known as pili, produce a simple tubular structure at the surface that transmits replicas of the plasmid to other bacteria. It has been demonstrated that plasmids play a key role in the transfer of traits with particular applications, 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.

Plasma Membrane

The 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 of the structure with bacteria, which gives them the ability to actively engage with their surroundings. Membranes have two sides, each with a different track and a distinct feature. They are highly organized and unsymmetrical. Membranes are dynamic and ever-changing and adjust to various environmental factors.


For microorganisms that possess them, flagella (plural, flagellum) are hair-like systems that enable for movement. A bacteria can have them across its surface or at one or both of its ends. To assist the bacterium in moving toward nutrients, away from harmful substances, or, in the instance of the symbiotic cyanobacteria, toward the light, the appendages beat in a turbine manner.


Chromosome DNA is found in a cytoplasmic area known as the nucleoid. The location of the DNA strands is just a region of the cytoplasm, not a membrane-bound nucleus. Although a few kinds of bacteria do contain two or more chromosomes, most microorganisms have a solitary, circular chromosome that is in charge of replication. smaller supplementary circular DNA strands.


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 building materials, including teeth, bowels, and rocks. Many illness microorganisms gradually lose their ability to transmit when they lack pili because they can’t connect to host tissue. For conjugation, two bacteria exchange plasmid DNA pieces through specialized pili.


They encode the gene sequence from the genomic language of nucleotides to that of amino acids—the basic building block of proteins. The molecules that carry out all of the tasks required by cells and other living things are called proteins. Eukaryotic ribosomes and bacterial ribosomes are similar, however bacterial ribosomes are smaller and have a marginally different molecular make-up. Microbial ribosomes are loose structures dispersed throughout the cytoplasm; they are never attached to other organelles, as they occasionally are (linked to the endoplasmic reticulum) in eukaryotes. Since bacterial and eukaryotic ribosomes differ sufficiently from one another, some antibiotics will prevent bacterial ribosomes from functioning but not eukaryotic ribosomes, kill the bacteria but not the eukaryotes they are associated with.

Frequently Asked Questions

Question 1: Which type of reproduction is seen in bacteria?


Bacteria can reproduce asexually or occasionally switch to sexual reproduction. They primarily use conjugation, which involves passing DNA from one bacterium to another, during sexual reproduction. In asexual reproduction, binary fission occurs.

Question 2: Why cyanobacteria is known as blue-green algae?


Chlorophyll, which would be found in the case of cyanobacteria, aids during photosynthetic, which raises the atmospheric oxygen concentration. Blue-green algae are however known as cyanobacteria.

Question 3: Archaebacteria could endure harsh environments due to the presence of ?


Due to their stiff cell walls, archaebacteria can withstand circumstances that most organisms cannot, such as extreme temps and salt concentrations.

Question 4: Which structure is useful for the monera for movements?


The primary function of the flagellum is to facilitate mobility also chemotaxis. Bacteria may have single or many flagellums. Therefore flagella would be used for movements.

Question 5: What is the use of carotenoids in bacteria?


The ability of bacteria to generate carotenoids is enormous. Carotenes were secondary plant metabolites that are essential for cell adaptation among heterotrophic bacteria. Carotenes participate in the mechanism of the fluidity of membrane and shield tissues against Uv rays and oxidative damage

Question 6: What would kingdom monera include?


There are only prokaryotic creatures in Kingdom Monera. There are species with only one cell. These were composed of a single cell enclosed by a cell membrane, and membrane-bound organelles such as mitochondria and Golgi bodies are absent. Additionally, they lack a real nucleus.

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Last Updated : 04 Nov, 2022
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