Monera - Classification , General characters , Examples
The Monera got status of phylum by Ernst Haeckel.
The kingdom Monera includes prokaryotes. Bacteria are the sole members of the Kingdom Monera. Organisms of kingdom monera are regarded as lower-level organisms and They have single cell in their body regulates all the functions of the body.
General Character of Kingdom Monera
1.They are microscopic and prokaryotic with primitive nuclei.
2.The nucleus is without a nuclear envelope, nucleolus, nucleoplasm, histone protein and true chromosomes.
3.Only DNA is present in the form of Nucleoid.
4.The cell wall is composed of peptidoglycan.
5.The members may be unicellular as in eubacteria and filamentous as in cyanobacteria.
6. These organisms may be motile or non-motile.
7. They are autotrophic, heterotrophic, parasitic or saprophytic.
8. The monerans are photoautotrophs like cyanobacteria or chemoautotrophs like Thiobacillus.
9. The mode of reproduction is by fission or budding. Sexual reproduction, mitosis, and meiosis are absent.
Bacteria are grouped into four categories based on their shape: 1. The bacteria in spherical shape are called Coccus. For Ex - Streptococcus. 2. The rod-shaped bacteria are Bacillus. For Ex - Lactobacillus
3. Vibrium are comma-shaped bacteria. For Ex- vibrio cholerae 4. The spiral shaped bacteria are termed Spirillum For Ex- Rhodospirillum.
Classification of Monera- Kingdom Monera is divided into two sub-kingdoms- Archaebacteria and Eubacteria.
Sub Kingdom Archaebacteria
They are the most abundant and cosmopolitan in nature. Bacteria are found everywhere even in such harsh climates where life is very difficult to survive but They survive in hot springs, deserts, snow and deep oceans etc. Many of them live in or on other organisms as parasites and some are decomposer or photosynthetic or chemotrophs or heterotrophs.
These groups of bacteria are primitive and supposed to have appeared around 4 to 5 billion years back. They adapted themselves to live in any harsh climate. These bacteria can live in extreme salty areas thus called halophiles.
They are also found in hot springs and marshy areas called thermoacidophiles and methanogens respectively.
Archaebacteria survive in harsh climates because of their special cell wall Which is made up of polysaccharides and protein. Due to the presence of special cell walls they differ from other bacteria.They have special pigment bacteriorhodopsin to perform photosynthesis hence they are autotrophs.
Archaebacteria are broadly classified into three types.
Methanogens: are responsible to release the methane while performing their metabolic activities. Methanogens are also present in the gut of several ruminant animals such as cows and buffaloes. They also produced biogas from the dung of animals in which methane is one of the important constituents. Methanogens can not survive in the presence of oxygen. Hence they can be found in swamp and marshes in areas in which all oxygen is consumed. The smell in these areas is due to the production of methane. For Example Methanobacillus, Thiobacillus
Thermoacidophiles are found in extremely hot and acidic climates and can also be found in hot springs. Most of the thermoacidophiles use hydrogen sulphide as their energy source. They precipitate bicarbonate into carbonate due to their activities. For Example Thermoplasma, Picrophilus, Thermococci, Pyrococcus, Sulfolobus
Halophiles are those that are found in salty environments like a great salt lake or dead sea. These environments are extremely basic. For Example - Halobacteria, halococcus,
Subkingdom Eubacteria:
There are true bacteria.They are featured by the presence of a rigid cell wall made up of Peptidoglycan or Murein. Their cell membrane contains lipids. If bacteria are motile like E. coli a flagella is present. The flagella are made up of protein flagellin. Some bacteria also contain short appendages like structures that are modification of the cell surface called pili. These pilli play a role in sexual reproduction and help to attach with the body of the host.
Eubacteria can be grouped into Gram-positive bacteria and Gram-negative bacteria on the basis of staining property.
Eubacteria are divided into following categories.
Actinomyces are gram-positive bacteria and found in soil. Sometimes they are considered as fungi. They produce commonly used antibiotics like streptomycin and tetracycline.
For Example - Streptomyces, Mycobacterium, Actinomyces,
Chemoautotrophs are chemosynthetic autotrophic bacteria.They oxidize inorganic substances like hydrogen sulphide, nitrates, nitrites, methane, and ammonia. During the oxidation of inorganic substances, they release energy in the form of ATP.
They are also involved in nutrient cycling or biogeochemical cycles like nitrogen, phosphorus, iron and sulphur. For Example Nitrobacter, Nitrosomonas,
Cyanobacteria also known as blue-green algae. they have chlorophyll similar to green plants hence called photosynthetic autotrophs.
The cyanobacteria are unicellular, colonial or filamentous, freshwater or marine or terrestrial algae.
The colonies are generally surrounded by a gelatinous sheath. They often form blooms in polluted water bodies.
Some of these organisms can fix atmospheric nitrogen in specialized cells called heterocysts,
For Ex- Anabaena, Nostoc, Oscillatoria, and Spirulina, etc.
Enterobacteria are gram-negative, rod-shaped bacteria and they are aerobic heterotrophs. They are pathogenic and cause diseases like bubonic plague and cholera. For Example - Salmonella, Vibrio Cholerae,
Pseudomonas are gram-negative bacteria and are rod shaped. They are heterotrophic bacteria and commonly found in soil. Some of them are pathogens to plants.
For Example Pseudomonas
Rickettsias and
Chlamydias:
They are small gram-negative bacteria. They are pathogens of human
For example - Rickettsia, Chlamydia
Spirochaetes are long and have a coil-shaped cell.They have flagella at both ends.They are commonly aquatic and pathogens. For Ex- Treponema
.
Comments
Post a Comment