Monera: Definition, Classification, Characteristics, Structure, Examples

Definition of Monera: The Monera is a unicellular prokaryotic organism comprising, but mainly consisting of, bacteria and archaea. If viewed using a microscope, it seems to have no true nucleus, unlike other membrane-bound organelles. The organisms of Kingdom Monerans divide through binary fission and can live in various environments, from soil and water to extreme conditions. Monera is a topic in the chapter Biological Classification in Biology.

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This Story also Contains

1. What is Kingdom Monera?
2. Kingdom Monera Characteristics
3. Classification of Monera
4. Bacteria: A Major Group in Monera
5. Role of Bacteria in the Environment
6. Economic Importance
7. Archaea: Unique Prokaryotes
8. Symbiotic Relationships
9. Pathogenic Bacteria
10. Laboratory Techniques for Studying Monera
11. Modern Applications of Monera
12. Recommended Video on Monera:

What is Kingdom Monera?

The five kingdoms of biological classification include Monera. It comprises unicellular and prokaryotic organisms. They can be either unicellular or multicellular. These are organisms with no true nuclei or membrane-bound organelles, a characteristic that demarcates them from the eukaryotic cells. Monera has a wide range of diversity in terms of shape and metabolic types. Since monera are found in almost all environments, they range from deep oceans to extreme hot springs.

The significance of studying the Monera organisms is that these microbes play very important roles almost in all ecological and biological operations that range from nutrient cycling, and decomposition to nitrogen fixation. They are, additionally, with high importance in medicine, agriculture, and industry whereby it spans antibiotic production to genetic engineering. They also offer knowledge helpful for the control of infectious diseases and new biotechnological developments.

Kingdom Monera Characteristics

The characteristics of monera are defined as:

Cell Structure

• Lack of a true membrane-bound nucleus and membrane-bound organelles.

• Cell wall composition is mostly of peptidoglycan.

• There is no nuclear membrane that encapsulates the genetic material.

• However, protein synthesis occurs in these ribosomes, which turn out to be smaller as compared to those of the eukaryotes.

• Involvement of the plasma membranes with mesosomes in cellular processes such as respiration and replication of DNA.

Genetic Material

Circular DNA molecule located within the nucleoid region, not membrane-bounded.

Small, circular pieces of DNA that are called plasmids replicate independently of the chromosomal DNA. Often these carry genes for antibiotic resistance and other functions.

Metabolism

The metabolism includes:

Autotrophic

• Use sunlight to synthesise food, e.g., cyanobacteria.

• Use chemical reactions to obtain energy, e.g., nitrifying bacteria.

Heterotrophic

• Decompose and absorb nutrients from dead organic matter.

• Obtain nutrients from living hosts, often causing disease.

Also read-

• MCQ Practice on Monera
• Biological Classification
• Cyanobacteria
• Structures in Bacteria

Classification of Monera

Monerans are classified based on various characteristics:

Based On Shape

• Cocci: Spherical-shaped bacteria.

• Bacilli: Rod-shaped bacteria.

• Spirilla: Spiral or corkscrew-shaped bacteria.

• Vibrios: Comma-shaped bacteria.

Based On Gram Staining

• Gram-positive

• Gram-negative

Based On Nutrition

Based on nutrition monera are classified as:

Autotrophs

Synthesise their food from inorganic substances.

Heterotrophs

Obtain their food from organic substances.

Based On Respiration

Based on the mode of respiration monera are classified as:

Aerobic

Require oxygen for respiration.

Anaerobic

Do not require oxygen for respiration and may even be poisoned by it.

Based On Reproduction

The different modes of reproduction are:

Binary fission

A process of asexual reproduction in which the cell just divides into two identical daughter cells.

Budding

A type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one specific site.

Endospore formation

A survival mechanism in which the bacterium produces a tough resistant spore in which to withstand unfavourable conditions.

Bacteria: A Major Group in Monera

The different types and examples of bacteria are classified as:

Archaebacteria

• Methanogens: These microbes produce methane as a byproduct of their anaerobic respiration.

• Halophiles: are found in extreme, high-salt environments like salt lakes and salt marshes.

• Thermoacidophiles: Opt for extremely high temperatures and acidity environments, as in the case of hot springs and volcanic vents.

Eubacteria

• Cyanobacteria are Photosynthetic bacteria that release oxygen as a photosynthetic by-product.

• Actinobacteria are filamentous. Ecologically important in decomposition.

Bacteria Diagram

The diagram given below shows the bacterial cell and its components

Role of Bacteria in the Environment

• Convert atmospheric nitrogen to ammonia, which can be used by plants.

• Break organic matter into simple compounds, hence this recycles nutrients.

• Use bacteria in the biodegradation of pollutants, hence these purify polluted environments through natural means.

Economic Importance

• Bacteria are used in the production of antibiotics such as penicillin and streptomycin. These are used in the treatment of bacterial infections in humans and domestic animals.

• They supply enzymes, vitamins, and other biochemicals that are used internally in industries.

• Bacteria in agriculture mainly aid in nitrogen fixation, in which atmospheric nitrogen is converted into forms available for the plants to grow on.

• Some bacteria-for instance, plant growth produce growth-promoting substances and protect plants from pathogens; they therefore promote the growth of plants.

• The process is very important in fermentation because bacteria, here, convert sugars into alcohol, acids, or gases.

• This therefore aids in the production of food products such as yoghurt, cheese, vinegar, and bread.

• They also improve the flavour and texture as well as the nutritional value of the food.

Archaea: Unique Prokaryotes

They are the extremophiles theoretically known to grow at high temperatures, high salt concentrations, and acidic or alkaline conditions.

Differences from Eubacteria

• Archaea possess unique cell-membrane lipids which are distinct from true bacteria.

• The molecular machinery of transcription and translation is more akin to the eukaryotes than the eubacteria.

• Unlike eubacteria that contain peptidoglycan, archaea do not have peptidoglycan in their cell walls.

Symbiotic Relationships

The symbiotic relationships exhibited by bacteria are:

Rhizobium in nitrogen fixation

• Forms symbiotic relationships with leguminous plants; for instance peas and beans.

• Fixes nitrogen from the air into ammonia, used by the plant to grow. The plant provides carbon and shelter to the bacteria.

Gut Bacteria in Humans and Ruminants

• Play an important role in the digestion of the host by degrading complex carbohydrates that the host is not able to carry out itself

• The microbes also synthesize vitamins and other compounds useful to the nutrition and good health of the host.

Biofilms

• Biofilms are communities of bacteria that they attach to through a self-produced extracellular polymeric substance EPS matrix.

• They develop on surfaces such as rocks, medical implants, and teeth, creating either beneficial as in wastewater treatment or detrimental for example dental plaques.

• Biofilms provide a very high degree of protection from antibiotics and immunological responses hence increased survival in hostile environments

Pathogenic Bacteria

Pathogenic bacteria cause several diseases in humans, which influence public health.

• Tuberculosis: This is caused by Mycobacterium tuberculosis. It mainly attacks the lungs. spots The general symptoms are chronic coughing, fever, and loss of weight.

• Cholera: This is caused by Vibrio cholerae. There is acute diarrhoea and dehydration that will lead to death unless treated.

• Typhoid: It is caused by Salmonella typhi.

• Pneumonia: Many cases are due to Streptococcus pneumoniae.

• Plant diseases: Plant diseases caused by pathogenic bacteria cause massive destruction to crops amounting to heavy agriculture losses.

• The excessive epidemic of bacterial blight in crops such as rice and beans, for instance, is one that massively impairs food production through symptoms such as wilting and leaf spots that lead to reduced yield.

Laboratory Techniques for Studying Monera

The laboratory techniques are described below:

Gram staining

Differentiates bacteria into Gram-positive (purple) and Gram-negative (pink) based on cell wall properties.

Acid-fast staining

Identifies acid-fast bacteria, such as Mycobacterium species, which retain the stain even after being washed with acidic alcohol.

Agar plates

The solid medium used to grow and isolate pure bacterial colonies.

Broth cultures

This is the liquid media suspension to grow bacteria. This gives large amounts of bacterial growth.

Light microscopy

The shape, size, and arrangement of bacteria are viewed by the use of visible light.

Electron microscopy

Provides detailed images of bacterial ultrastructure with higher magnification and resolution using electron beams.

Modern Applications of Monera

Especially bacteria, Monera play a very critical role in genetic engineering. Recombinant DNA technology is associated with inserting foreign genes into bacterial plasmids. This way, bacteria produce useful proteins like insulin and human growth hormones. Now, precise DNA modifications can be made using the CRISPR-Cas9 system that is derived from bacterial systems. This is now being hailed as a revolutionary genetic research and therapy tool.

Bacteria have several applications in biotechnology. For instance, bacteria are used in producing insulin used in treating diabetes. This is done by inserting the human insulin gene into bacterial plasmids. Other applications of bacteria in biotechnology include the production of biodegradable plastics. These plastics result from the action of bacteria that produce polyhydroxyalkanoates, PHA. This is a more environmentally friendly alternative to conventional plastics.

Also Read-

Recommended Video on Monera: