Key Features & Classification of Kingdom Monera
It is exceptionally astonishing to realize that microbes alone possess a total realm in the progressive system of living life forms. They are the ubiquitous life forms of the living scene. We can discover microscopic organisms all over. This property can be owed to the way that microbes have a wide scope of the assortment, and a large number of them are adjusted to make do in outrageous natural conditions. An enormous number of microscopic organisms likewise live on different living beings as parasites. The organisms that belong to this kingdom are usually unicellular and are mostly found in a moist environment.
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Characteristics of Monera
The characteristics of the organisms belonging to this kingdom include: -
The Monerans are unicellular organisms.
The cell wall is rigid and made up of peptidoglycan.
Asexual Reproduction through binary fission.
They contain 70S ribosomes.
Flagella serves as the locomotory organ.
It lacks organelles like mitochondria, lysosomes, plastids, Golgi bodies, endoplasmic reticulum, centrosome, etc.
These are environmental decomposers and mineralizers.
Bacteria
Bacteria are regarded as microscopic organisms that have the ability to survive in diverse environments. They could be both beneficial as well as harmful in certain ways. They usually have a simple structure without a nucleus and with a few cell organelles. The bacteria are generally surrounded by two protective coverings, mainly the outer cell wall and the inner cell membrane. Some bacteria are also covered with a capsule. A few of the bacteria like mycoplasma do not possess a cell wall.
The short whip-like structures called the pili are the extensions that surround the surface of the bacteria. The long whip-like structures are also present on the surface called flagella. They exhibit both autotrophic and heterotrophic modes of nutrition. Autotrophic bacteria are the ones that derive nutrition from the inorganic substances, and they take in the carbon and hydrogen from the atmospheric carbon dioxide, including H2, H2S, and NH3.
Structure of Bacteria
The important features of the bacterial structure are mentioned below.
Capsule: A slimy capsule is generally present outside the cell wall of a large number of bacteria. This capsule is composed of polysaccharides and nitrogenous substances like amino acids. This slime layer becomes thick to take the shape of a capsule.
Cell wall: All the bacterial cells are often covered by a strong, rigid cell wall. The cell wall is present inside the capsule.
Plasma Membrane: Each bacterial cell contains a plasma membrane. It is situated just internal to the cell wall, and it is a thin, elastic membrane that is differentially or selectively permeable.
Cytoplasm: The cytoplasm is a complex and aqueous fluid or semi-fluid ground substance that is present in the bacteria.
Nucleoid: The nucleus is present in the bacteria, and they are surrounded by some typical proteins that are not histone proteins.
Plasmids: Along with the normal DNA chromosomes, many bacteria also have extrachromosomal genetic elements or DNA. These elements are called plasmids.
Flagella: These are fine, thread-like, protoplasmic attachments. They extend through the cell wall and the slime layer of the flagellated bacterial cells. They help the bacteria to swim in the liquid medium.
Pili or Fimbriae: Apart from flagella, some tiny or small hair-like outgrowths are also present on the bacterial cell surface, which are called pili.
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Bacterial Shape
There are several types of bacterial structure, which are described below.
Bacilli- These are rod-shaped bacteria with or without flagella.
Cocci- These bacteria are spherical or oval in shape. These can be micrococcus (single), diplococcus (in pairs), tetracoccus (in fours), streptococcus (in chains), and staphylococcus (in clusters like grapes).
Spirillum- These are spiral or coiled-shaped bacteria. They are rigid due to the spiral structure and bear flagella at one or both ends.
Vibrios- These are commas or small kidney-shaped bacteria with flagella on one end.
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Classification of Monera
There are three classes of Monera namely: archaebacteria, eubacteria and cyanobacteria.
Archaebacteria
These are some of the most ancient bacteria that were found in extreme habitats like hot springs, salty areas, and marshy areas.
The structure of the cell wall is unlike the other bacteria that help them survive in extreme conditions.
They use the autotrophic mode of nutrition.
Their nucleotide sequences of tRNA and rRNA are unique
Eubacteria
They are known as "true bacteria."
They have a rigid cell wall as it is made up of peptidoglycans.
It uses flagella for movement.
They have pili on their surface that help them to stick on the surface of the host.
They can be divided into two categories, namely gram-positive and gram-negative.
Examples of eubacteria include rhizobium and clostridium.
Cyanobacteria
They are blue-green algae.
They are photosynthetic in nature.
They are usually found in the aquatic region.
They also play a role in fixing atmospheric nitrogen.
Examples include Anabaena, nostoc, spirulina etc.
To conclude the article we have learned about the features and classification of Monera along with their structure.
FAQs on Kingdom Monera Explained: Full Guide for Students
1. What is Kingdom Monera, and what types of organisms does it include?
Kingdom Monera is a biological kingdom that includes all prokaryotic organisms. These are typically single-celled life forms that are defined by the absence of a true, membrane-bound nucleus. The primary organisms in this kingdom are bacteria, which are further divided into groups like Archaebacteria and Eubacteria, as well as cyanobacteria (also known as blue-green algae).
2. What are the key characteristics that define an organism in Kingdom Monera?
Organisms belonging to Kingdom Monera share several defining characteristics that distinguish them from eukaryotes. These include:
Cellular Structure: They are unicellular and prokaryotic.
Genetic Material: Their DNA is not enclosed in a nucleus but is located in a region called the nucleoid.
Organelles: They lack complex, membrane-bound organelles such as mitochondria, chloroplasts, and the endoplasmic reticulum.
Cell Wall: Most possess a rigid cell wall made of peptidoglycan.
Ribosomes: They contain 70S ribosomes for protein synthesis.
Reproduction: The primary mode of reproduction is asexual, mainly through binary fission or budding.
3. How is Kingdom Monera classified into major groups?
Kingdom Monera is broadly classified into two main sub-kingdoms based on significant differences in their cell structure and habitat. These groups are:
Archaebacteria: Often referred to as 'ancient bacteria', these organisms are known for thriving in extreme environmental conditions. Examples include methanogens (methane-producers), halophiles (salt-lovers), and thermoacidophiles (heat and acid-lovers).
Eubacteria: Known as 'true bacteria', this group comprises the vast majority of bacteria found in common environments. This category includes common bacteria and photosynthetic organisms like cyanobacteria.
4. What are the different types of nutrition found in Kingdom Monera?
Monerans exhibit the most diverse modes of nutrition of any kingdom. The main types are:
Autotrophic: Organisms that synthesise their own food. This includes photoautotrophs, which use light energy (e.g., cyanobacteria), and chemoautotrophs, which use energy from chemical reactions (e.g., nitrifying bacteria).
Heterotrophic: Organisms that obtain energy from external organic compounds. This includes saprophytes (feeding on dead organic matter), parasites (living on or inside a host), and symbionts (living in a mutually beneficial relationship).
5. What is the fundamental difference between Archaebacteria and Eubacteria?
The most fundamental difference between Archaebacteria and Eubacteria lies in their cell wall composition and cell membrane structure. Eubacteria have cell walls composed primarily of peptidoglycan, a polymer essential for their structural integrity. In contrast, Archaebacteria lack peptidoglycan and possess cell walls made of different proteins and polysaccharides. This structural distinction is what allows Archaebacteria to survive in extreme environments that are inhospitable to Eubacteria.
6. Why is Kingdom Monera considered so important for the ecosystem?
The importance of Kingdom Monera is immense because its members serve as the primary decomposers and mineralizers in almost every ecosystem. They break down complex organic waste and the remains of dead organisms, recycling essential nutrients like carbon, nitrogen, and phosphorus back into the environment. Without this recycling process, nutrients would remain locked in dead matter, and ecosystems would collapse. Furthermore, certain bacteria like Rhizobium are crucial for nitrogen fixation, converting atmospheric nitrogen into a form that plants can absorb.
7. How do organisms in Kingdom Monera perform essential functions like respiration without mitochondria?
Monerans compensate for the lack of complex organelles like mitochondria by using their cell membrane. The cell membrane is folded inwards to increase its surface area and contains the necessary enzymes and electron transport chains to carry out cellular respiration and generate energy (ATP). In photosynthetic monerans, these infoldings, called chromatophores, contain photosynthetic pigments and function similarly to the thylakoids within a chloroplast. This makes the cell membrane a multi-functional site for many vital metabolic processes.
8. What are some common examples of Monerans and their practical importance to humans?
Many monerans have significant practical applications for humans. Some important examples include:
Lactobacillus: A bacterium used in the food industry for the fermentation of milk to produce curd, yoghurt, and cheese.
Streptomyces: A genus of bacteria that is a major source for the production of antibiotics used in medicine.
Escherichia coli (E. coli): While some strains are pathogenic, E. coli is a vital tool in biotechnology and genetic engineering for producing insulin and other therapeutic proteins.
Rhizobium: A nitrogen-fixing bacterium that forms a symbiotic relationship with legume plants, naturally enriching the soil and reducing the need for chemical fertilisers in agriculture.
