Kingdom Monera
Kingdom Monera - All the organisms of this kingdom are prokaryotes. Complex structure was the basis of classification of organisms, many centuries ago. According to R.H. Whittaker's five kingdom classification all the bacteria were placed under the Kingdom Monera.
Monera are considered as the most primitive group of organisms. They include various types of bacteria and blue-green algae.
Monerans are most abundant of all organisms, due to their versatility of their habitat.It is estimated that a single drop of water contains 50 billion bacteria.
The Kingdom Monera includes organisms that are single-celled known as bacteria. The microorganisms in Kingdom Monera are considered as the most ancient living forms on earth. The kingdom is divided into two groups Archaebacteria and Eubacteria. All the organisms of this kingdom are prokaryotes. These cells do not have nuclear membrane, the chromosome is a single and circular, they also lack membrane bound cellular organelles. This kingdom includes bacteria, cyanobacteria, mycoplasma etc. They are unicellular organisms and do not have specific mode of nutrition. They can be either aerobic or anaerobic.These organisms have cell wall which is made up of peptidoglycans. The cell organelles are not membrane bound. Cell organelles like endoplasmic reticulum, mitochondria are absent. Reproduction is by spore formation and binary fission.
The Kingdom Monera includes organisms that are single-celled known as bacteria. The microorganisms in Kingdom Monera are considered as the most ancient living forms on earth. The kingdom is divided into two groups Archaebacteria and Eubacteria. All the organisms of this kingdom are prokaryotes. These cells do not have nuclear membrane, the chromosome is a single and circular, they also lack membrane bound cellular organelles. This kingdom includes bacteria, cyanobacteria, mycoplasma etc. They are unicellular organisms and do not have specific mode of nutrition. They can be either aerobic or anaerobic.These organisms have cell wall which is made up of peptidoglycans. The cell organelles are not membrane bound. Cell organelles like endoplasmic reticulum, mitochondria are absent. Reproduction is by spore formation and binary fission.
General characteristics of the kingdom Monera are as follows:
- They are primitive organisms.
- All organisms of the kingdom are prokaryotes.
- They are present in both living and non-living environment.
- They can survive in harsh and extreme climatic conditions like in hot springs, acidic soils etc.
- They are unicellular organisms.
- Membrane bound nucleus is absent.
- DNA is in double stranded form, suspended in the cytoplasm of the organism,referred as nucleoid.
- A rigid cell wall is present.
- Membrane bound cellular organelles like mitochondria are absent.
- Habitat - Monerans are found everywhere in hot springs, under ice, in deep ocean floor, in deserts and on or inside the body of plants and animals.
- Nutrition - autotrophs - can prepare their own food, heterotrophs - depend on others for food, saprophytes - feed on dead and decaying matter, parasitic - live on other host cells for survival and cause, symbiotic - in mutual relation with other organisms, commensalism - it is where one organism is benefited and the other is not affected, mutualism - where both the organisms are benefited.
- Respiration - respiration in these organisms vary, they may be obligate aerobes - the organisms must have organisms for survival; obligate anaerobes - the organisms cannot survive in the presence of oxygen; facultative anaerobes - these organisms can survive with or without oxygen.
- Circulation - is through diffusion.
- Movement - is with the help of flagella.
- Reproduction is mostly asexual, sexual reproduction is also seen. Asexual reproduction is by binary fission, sexual reproduction is by conjugation, transformation and transduction.
Classification of Kingdom Monera
Kingdom Monera has been classified into two groups - Archaebacteria and Eubacteria.
Archaebacteria are microbes that live in extreme and harsh conditions, they are known as extremophiles. These bacteria lack cell wall, their cell membrane is made up of different lipids, and their ribosomes are similar to that of eukaryotes.
Archaebacteria are of three major groups of bacteria based on their habitat i.e., thermophiles, halophiles and methanogens.
Some extremophiles live in boiling water like geysers of Yellowstone National Park and and in volcanoes. These are known as 'thermophiles'.
Some extremophiles live in extremely salty water, the salt loving bacteria are known as 'halophiles'.
Some bacteria are present in the guts of ruminants and are responsible for production of methane gas from their dung. These bacteria are known as 'methanogens'.
Eubacteria are true bacteria. The characteristic feature is the presence of rigid cell wall and if present a motile flagelllum that aids in locomotion.These organisms are characterized based on their nutrition and their shapes.
Classification based on Shape
Classification Based on Mode of Nutrition
Archaebacteria are microbes that live in extreme and harsh conditions, they are known as extremophiles. These bacteria lack cell wall, their cell membrane is made up of different lipids, and their ribosomes are similar to that of eukaryotes.
Archaebacteria are of three major groups of bacteria based on their habitat i.e., thermophiles, halophiles and methanogens.
Some extremophiles live in boiling water like geysers of Yellowstone National Park and and in volcanoes. These are known as 'thermophiles'.
Some extremophiles live in extremely salty water, the salt loving bacteria are known as 'halophiles'.
Some bacteria are present in the guts of ruminants and are responsible for production of methane gas from their dung. These bacteria are known as 'methanogens'.
Eubacteria are true bacteria. The characteristic feature is the presence of rigid cell wall and if present a motile flagelllum that aids in locomotion.These organisms are characterized based on their nutrition and their shapes.
Bacteria can be classified in four groups based on shape : Spherical or round shaped bacteria are called cocci, Rod-shaped are bacilli, Comma-shaped bacteria are vibrio and spiral shaped bacteria are spirilla.
Based on the mode of nutrition bacteria are broadly classified into Autotrophic and Heterotrophic.
Autotrophic bacteria - Bacteria which prepare their own food are autotrophic. (Example Cyanobacteria)
Heterotrophic bacteria - Bacteria which are dependent on other organisms for their food are heterotrophic.(Example Escherichia coli)
Autotrophic bacteria can be Chemosynthetic or Photosynthetic.
Chemosynthetic bateria are those which prepare their food with the help of inorganic substrates. Photosynthetic bacteria are autotrophic bacteria which prepare their own food by the process of photosynthesis.
Cyanobacteria (Blue-green algae) - They have chlorophyll similar to plants and hence they are photosynthetic autotrophs. The marine and terrestrial and they may be unicellular, colonial or filamentous. The colonies are surrounded by gelatinous sheath. They can also fix atmospheric nitrogen.
Example: Nostoc and Anaebena.
Chemosynthetic autotrophs - these organisms oxidise substances like nitrites, nitrates, ammonia etc. The help in recycling substances like nitrogen, sulphur, iron etc.
Chemosynthetic bateria are those which prepare their food with the help of inorganic substrates. Photosynthetic bacteria are autotrophic bacteria which prepare their own food by the process of photosynthesis.
Cyanobacteria (Blue-green algae) - They have chlorophyll similar to plants and hence they are photosynthetic autotrophs. The marine and terrestrial and they may be unicellular, colonial or filamentous. The colonies are surrounded by gelatinous sheath. They can also fix atmospheric nitrogen.
Example: Nostoc and Anaebena.
Chemosynthetic autotrophs - these organisms oxidise substances like nitrites, nitrates, ammonia etc. The help in recycling substances like nitrogen, sulphur, iron etc.
Heterotrophic bacteria are those which are dependent on other organism either directly or indirectly for their nutrition. They are most abundant and are important decomposers. Some are helpful in curdling milk, production of antibiotics, in nitrogen fixation and some are pathogens.
Heterotrophic bacteria can be parasitic and saprophytic. Parasitic bacteria are those which depend on the host for nutrition and cause harm to the host. Saprophytic bacteria feed on dead and decaying matter.
Heterotrophic bacteria can be parasitic and saprophytic. Parasitic bacteria are those which depend on the host for nutrition and cause harm to the host. Saprophytic bacteria feed on dead and decaying matter.
Symbiotic - it is a type where the bacteria are in mutual relation with other organisms. Symbiosis is of two types mutualism and commensalism. Mutualism is where the bacteria and the other organism are benefited due to the relationship. Commensalism is a relationship where the bacteria is benefited while the other organism is not affected by the relationship.
Classification based on Gram's staining
Gram's staining is a test on cell walls developed by Hans Christian Gram. This method helps classifying bacteria into Gram positive bacteria and Gram negative bacteria.
Gram Positive Bacteria - The bacteria's cell wall is made up of protein-sugar complex that takes on purple color during gram staining.
Classification based on Gram's staining
Gram's staining is a test on cell walls developed by Hans Christian Gram. This method helps classifying bacteria into Gram positive bacteria and Gram negative bacteria.
Gram Positive Bacteria - The bacteria's cell wall is made up of protein-sugar complex that takes on purple color during gram staining.
Gram Negative Bacteria - The gram negative bacteria has an extra layer of lipid on the outside of the cell wall and appear pink during the Gram staining procedure.
Reproduction in Bacteria
Bacteria usually reproduce by asexual method.
Binary fission
The nuclear material becomes enlarged and divides into two parts. Constriction is made in the middle of the cell on the cell membrane dividing cytoplasm into two parts. Ultimately, a cell is divided into two daughter cells. This method is very common and simplest method of reproduction in bacteria. By this method, about 2500,000 bacterial cells are produced in an hour.
Budding
During the process, small bud is developed on outer side of bacteria cell with cytoplasm. The bud gets enlarged and separated from mother cell.
Gonidia
In cell nuclear material and cytoplasm divides and arranged forming a tiny bodies. Each body having cell wall, cytoplasm and genetic material is called gonidium, which releases out and germinate to produce new bacterial cell.
Endospore
Under unfavorable condition a round spore is formed in the bacterial cell which is thick walled and highly resistant. The spore is oval or spherical called endospore. During endospore formation, the genetic material gets divided into two parts. One part migrates at one end of the bacterial cell. The cytoplasm is constricted at that end by constriction of cell membrane. A spore is then formed at that end. It releases out in the soil and may remain viable for several years. Under favorable condition, it germinates to produce new bacterial cells.
Sexual reproduction
The recombination of genes of bacterial cells through different ways from one to another cell is considered as the sexual reproduction. This is of following types
Transformation
The process of entrance of exogenous DNA from one bacterial cell to another cell is called transformation. The cell which gives exogenous DNA is called donor ant the cell which take is called recipient.
Transduction
The process in which genetic material from one bacterial cell transfers to another bacterial cell by means of viruses is called transduction. The virus evolve in this process is called bacteriophage.
Conjugation
The process in which two bacterial cells conjugate with the help of pili is called conjugation. During the process one bacterial cell transfer the chromosomal segments to another bacterial cell.
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