Characteristics and Classification of Monera

The Kingdom Monera is composed of unicellular and prokaryotic organisms, mainly bacteria. The word 'Monera' means single or solitary.' R.H. Whittaker placed Monera kingdom on the top in his widely accepted five-kingdom classification. The species in this kingdom are prokaryotes, lacking a well-defined nuclear membrane and cell organelles.

Bacteria are the most common members of the Monera kingdom. Monerans are an important biological classification that lack a true nucleus. In this article we will study the main characteristics and classification of Monera in more detail.

---

Kingdom Monera

[Click Here for Sample Questions]

Kingdom Monera only includes prokaryotic, simplest, and rudimentary organisms. Bacteria are the only members of this kingdom. However, there are several types of bacteria. The salient features of Kingdom Monera from other kingdoms are as follows:

• They are generally found in moist environments.
• They do not carry a nuclear envelope. Their genetic material consists only of naked circular DNA.
• They lack sap vacuoles. However, they contain gas vacuoles.
• The majority of Kingdom Monera members get nutrients through absorption.
• Few members of monera might be photosynthetic or chemosynthetic.
• They might be motile or non-motile. Motile organisms use flagella for movement.
• They have 70s ribosomes.​

---

Characteristics of Monera 

[Click Here for Sample Questions]

Organelles such as mitochondria, lysosomes, plastids, Golgi bodies, endoplasmic reticulum, centrosome, and others are not present. The organisms in this kingdom have the following characteristics:

• Monerans are single-celled creatures.
• The cell wall is made up of peptidoglycan and is stiff.
• Binary fission is asexual reproduction.
• They have 70S ribosomes in them.
• The locomotory organ is the flagella.
• These are decomposers and mineralizers for the environment.

---

Bacteria

[Click Here for Sample Questions]

Bacteria are small organisms that may thrive in a variety of conditions. They can be both beneficial and harmful. They have a basic structure that does not have a nucleus and only a few cell organelles.

• The outer cell wall and the inner cell membrane are two protective coverings that enclose the bacteria.
• A capsule also protects some germs. Only a few bacteria, such as Mycoplasma, lack a cell wall.
• Pili are short whip-like projections that encircle the bacteria's surface.
• Flagella are the long whip-like structures that make up a cell's membrane. 
• They eat in both autotrophic and heterotrophic ways.
• Inorganic compounds provide sustenance to autotrophic microorganisms.
• Carbon and hydrogen are obtained from ambient carbon dioxide, H₂, H₂S, and NH₃.
• For feeding, heterotrophic bacteria rely on organic elements from the outside world.
• Saprotrophs, parasites, and symbionts are examples of these.

---

Bacterial Shape

[Click Here for Sample Questions]

The bacterial shape includes

• Bacilli: Bacilli are rod-shaped bacteria that have or do not have flagella.
• Cocci: Cocci are bacteria that have a spherical or oval form. Micrococcus (single), diplococcus (in pairs), tetracoccus (in fours), streptococcus (in chains), and staphylococcus (in chains) are examples of these bacteria (in clusters like grapes).
• Stalked: A bacterium with a stalk is known as a stalked bacterium.
• Spirillum: Spirillum bacteria have a spiral or coiled form. Because of their spiral form, they are stiff and have flagella on one or both ends.
• Filament: These bacteria's bodies are made up of tiny filaments.
• Vibrios: Vibrios are little kidney-shaped bacteria with flagella on one end or commas.
• Budded: The body of such a bacterium is swollen in places.

---

Structure of Monera

[Click Here for Sample Questions]

Monerans are prokaryotic unicellular organisms that contain some cell structures such as cell wall, flagella, plasmids, etc. The distinctive features of the structures present in Monera or bacteria are discussed below:

Capsule

A slimy capsule can be found outside the cell wall of a large number of bacteria. Polysaccharides make up the majority of it, but nitrogenous compounds (amino acids) are also present.

• This slime layer thickens and is referred to as a capsule.
• Capsulated or pathogenic bacteria are bacteria that have formed a capsule.
• Bacillus anthracis, Diplococcus pneumoniae, and Mycobacterium tuberculosis are all parasitic forms of the capsule.

Cell Wall

A thick, stiff cell wall surrounds all bacterial cells. As a result, they are classified as plants. The cell wall is present within the capsule. Polysaccharides, proteins, and lipids make up this substance. 3D-glutamic acid and diaminopimelic acid are also present.

Plasma Membrane

A plasma membrane is found on each bacterial cell. It's located on the inside of the cell wall. It's a thin, elastomeric membrane that's also differentially or selectively permeable.

Cytoplasm

A complex and watery fluid or semi-fluid ground substance is referred to as cytoplasm (matrix). Vitamins, salts, enzymes, carbohydrates, soluble proteins, coenzymes, lipids, minerals, and nucleic acids make up this substance.

• Organic materials can be found in colloidal form.
• The presence of a significant number of ribosomes causes the cytoplasm to be granular.

Nucleoid

Other names for it include genophore, bare nucleus, and incipient nucleus. These contain nuclear material, as well as DNA. It is both double-helical and circular. It is surrounded by a typical protein. These are not, however, histone proteins.

Plasmids

Many bacteria (such as E.coli) include extrachromosomal genetic components of DNA in addition to their conventional DNA chromosomes. Plasmids are the elements in question. They're little double-stranded circular molecules.

Flagella

These are protoplasmic appendages that are fine and thread-like. The flagellated bacterial cells' cell wall and slime layer are penetrated by these. These aid bacteria in swimming in the liquid medium.

Pili or Fimbriae

On the bacterial cell surface, there are some microscopic or small hair-like outgrowths in addition to flagella. This is a pili. They're made up of pilin protein. As a result, they're around 0.5-2 mm long and 3-5 mm in diameter.

---

Classification of Monera

[Click Here for Sample Questions]

Monerans are extremely beneficial organisms. They are beneficial to the soil and play a crucial role in the nitrogen cycle. They're also helpful in the manufacturing of a variety of foods and medications. The only member of the kingdom monera, bacteria can be divided into three types based on their mode of nutrition.

Archaebacteria

These are the oldest bacteria that may be found in the most extreme environments, such as salty places (halophiles), hot springs (thermoacidophiles), and marshy locations (thermoacidophiles) (methanogens).

• The structure of the cell walls of these bacteria varies from that of the other bacteria, allowing them to thrive even in harsh environments.
• Autotrophic nutrition is the mode of nourishment.
• Its tRNA and rRNA nucleotide sequences are unique.

Eubacteria

Eubacteria is also referred to as "real bacteria."

• Peptidoglycans form the stiff cell wall.
• Flagella are used to assist it to move.
• A few bacteria have pili, which are small appendages on the cell surface that aid the bacteria in sexual reproduction.
• Pili also aids in the attachment of pathogens to their hosts.
• Depending on the type of the cell wall and the stain they take, they are classified as gram-positive or gram-negative.
• Two eubacteria are Rhizobium and Clostridium.

Cyanobacteria

Blue-green algae is another name for them.

• Photosynthetic microorganisms are found in nature.
• Chlorophyll, carotenoids, and phycobilins are all found in them.
• They can be found only in the water.
• Some of them are able to fix aerobic nitrogen.
• Cyanobacteria include Nostoc, Anabaena, and Spirulina.

---

Things to Remember

• The Kingdom Monera is composed of unicellular and prokaryotic organisms, mainly bacteria.
• Bacteria are the most common microbes and the only members of the Monera kingdom.
• Zoology is the branch of science that studies the salient features and classification of Monera.
• Kingdom Monera only includes prokaryotic, simplest, and rudimentary organisms.
• The majority of Kingdom Monera members get nutrients through absorption. However, some might be photosynthetic or chemosynthetic.
• Bacteria are small organisms that may thrive in a variety of conditions.
• A complex and watery fluid or semi-fluid ground substance is referred to as cytoplasm (matrix).