Salient features of the Kingdom Monera: Definition, Characteristics, Structure ...

The Kingdom Monera includes prokaryotic bacteria and cyanobacteria, among some of the oldest forms and diverse organisms on the Earth. Monera plays very significant roles in ecosystems from nutrient cycling to symbiotic relationships with higher organisms.

Definition of Kingdom Monera

The Kingdom Monera includes a vast array of organisms. All of these organisms are prokaryotic in their cellular structure, meaning that their cells lack membrane-bound organelles and do not have an obvious nucleus. These primarily comprise bacteria and cyanobacteria. Members can be found widely distributed in almost every environment on Earth, from deep-sea vents to the human intestines. Because they lack complexity, their very important ecological roles are often overlooked. They provide nutrient cycling, as well as participate in biogeochemical processes. The research on Monera provides knowledge of the general principles of cellular biology and microbiology. At the same time, it helps elaborate upon the evolutionary perspective and practical use of the Monera in biotechnology to medicine.

Historical Perspective

The classification of Kingdom Monera has changed a lot with time. As proposed by Ernst Haeckel way back in the late 19th century, initially, Monera was a kingdom of all unicellular organisms that lacked a distinct nucleus and thus included both bacteria and cyanobacteria. Later on, microbiology and molecular biology, have shown to be significantly different in these groups bringing about an automatic separation of -at least archaea from bacteria in the late 20th century. This reclassification provided evidence that there were divergent lines among prokaryotes and changed our understanding of microbial diversity. Today, we know Monera as one contiguous account of early Earth history, huge diversity, and modern relevance in ecological studies, among others, biotechnology and medicine.

Structural Features of Monera

• Cell Wall is made up of peptidoglycan in bacteria which is absent in archaea.

• The cell membrane encloses the cytoplasm, enclosing the passage of substances in and out of the cell.

• The cytoplasm contains genetic material and cellular machinery for metabolising processes.

• Ribosomes are sites for protein formation within the cytoplasm.

• Examples are cocci (spherical), bacilli (rod-shaped), and, spirilla (spiral).

• They can aggregate into chains, bunches (staphylococci), or pairs (diplococcus).

• Flagella are long, whip-like and propeller-like organs that help cell movements.

• Pili are Shorter append.

Monera Diagram

Given below is the diagram of a monera cell showing its components

Characteristics of Kingdom Monera

• Kingdom Monera embraces the most abundant organisms that are found in almost every habitat.

• They are unicellular and prokaryotic organisms.

• They lack the true nucleus bounded by a nuclear membrane nucleolus, instead have the naked, circular DNA folded to form nucleoid.

• Moneran possesses naked DNA which is not associated with proteins

• The Cell wall is made up of peptidoglycan

• Membrane-bound cell organelles like mitochondria, Golgi complex, endoplasmic reticulum etc are absent in monerans

• These organisms have the 70 S type of Ribosome.

• Reproduction in these organisms mainly occurs by asexual means i.e. binary fission, endospore production etc.

• Monerans may be autotrophic, saprotrophic, parasitic and chemoautotrophic.

Metabolic Diversity in Monera

Overall, Monera as a group displays varied nutritional modes. There are autotrophic bacteria that produce their food by utilising the energy from sunlight or carbon dioxide. Cyanobacteria which form symbiotic relationships with fungi develop into lichens. Chemosynthetic bacteria harvest energy through chemical reactions, usually in places where sunlight doesn't get in. Heterotrophic bacteria are those that derive their energy by breaking down organic material from the environment or hosts.

Key metabolic pathways for Monera include glycolysis conversion of glucose to pyruvate to produce ATP. In the absence of oxygen, this is followed by fermentation, whereby the pyruvate product is converted to one of several products, such as lactate or ethanol, to regenerate NAD+ that can be recycled in the glycolytic production of ATP. These pathways underscore the ability of the Monera to thrive under a range of environmental conditions and their importance in global nutrient cycling.

Reproduction and Genetic Diversity

Bacteria are organisms that mainly reproduce via binary fission. This means that every different bacterial cell will split into two or more identical daughter cells. In this type of asexual reproduction, replication of the bacterial chromosome occurs, followed by cellular elongation and, finally the cell splits into two - each cell containing a copy of the genetic material.

Genetic diversity in bacteria is brought about by horizontal gene transfer. Transformation takes up foreign DNA from the environment. Direct transfer of genetic material between different bacteria occurs by conjugation. In transduction, a bacteriophage or virus infects bacteria and carries DNA from one cell to another.

Examples of Monera

Members of the kingdom Monera are of the following types:

Eubacteria (True Bacteria)

• They are the largest and the most varied Kingdom Monera.

• They have cell walls composed of peptidoglycan and their metabolic ability ranges from photosynthesis to fermentation.

• They live symbiotically with plants and animals and, in a free-living state occupy many different ecosystems.

Archaebacteria (Ancient Bacteria)

• The archaebacteria are unrelated to eubacteria, and many archaebacteria live in extreme environments like hot springs, salty lakes, and deep-sea hydrothermal vents.

• They have unique cell membrane lipids and different ribosomal proteins from all other organisms.

• Archaebacteria also hold critical clues to Earth's early environmental conditions and to the evolution itself.

Cyanobacteria (Prokaryotic, Blue-Green Algae)

• These are photosynthetic bacteria that generate oxygen as they carry out photosynthesis.

• Hence ecologically, they play a vital role in the aquatic environment as primary producers and also fix nitrogen in some species.

• These group together and cause harmful algal blooms in nutrient-rich waters.

Mycoplasma (Wall-less Monerans)

• What makes Mycoplasma unique among bacteria is that they do not have a cell wall; as a result, they are considered pleomorphic.

• They are parasites or commensals and often infect plants and animals and cause diseases in human beings like pneumonia.

• Species of the genus Mycoplasma have some of the smallest genomes among free-living organisms, reflecting their adaptation to parasitic lifestyles.

Conclusion

They encompass a wide range of prokaryotic microorganisms such as bacteria, cyanobacteria, and archaebacteria. Ecologically, they are of great significance in nutrient cycling, symbiosis, and as primary producers. The medical, agricultural, and biotechnological applications of the Monera attest to the importance of this group to human health, environmental quality, and a range of industrial processes. The broad spectrum of metabolic pathways, reproductive strategies, and genetic adaptability of the Monera provide some valuable insights into the basic principles of microbial existence and the role of microorganisms in global ecosystems.

The video describing the features of Monera is given below: