Kingdom
Monera Characteristics
General characteristics of the kingdom Monera
are as follows:
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- 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.
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.
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
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.
Classification
Based on Mode of Nutrition
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 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.
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.
