Monera - Classification , General characters , Examples

Overview

• 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

• They have single cell or cellular body organisation in their body regulates all the functions of the body.

General Character of Kingdom Monera

• They are microscopic and prokaryotic with primitive nuclei.

• The nucleus is without a nuclear envelope, nucleolus, nucleoplasm, histone protein and true chromosomes. 

• Only DNA is present in the form of Nucleoid.

• The cell wall is non cellulosic composed of polysaccharides and amino acids.

• The members  may be unicellular as in eubacteria and filamentous as in cyanobacteria.

• These organisms may be motile  or non-motile.

• They are autotrophic, heterotrophic, parasitic or saprophytic but the majority of bacteria are heterotrophic.

• The monerans are photoautotrophs like cyanobacteria or chemoautotrophs like  Thiobacillus.

• The reproduce mainly by fission but in some conditions they form spore for the reproduction.

• In unfavourable condition , they transfer their DNA from one bacteria to another. Sexual reproduction, mitosis, and meiosis are absent.

Categories of Bacteria on the basis of their shape.

• Bacteria are grouped into four categories based on their shape:

• The bacteria in  spherical shape are called Coccus. For Ex - Streptococcus. 2. The rod-shaped bacteria are  Bacillus. For Ex - Lactobacillus

• 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.

Microbes used in formation of Biogas

• 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

• They 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 - Streptomycin Mycobacterium, Actinomyces, 

How are microbes used in formation of Antibiotics

Chemoautotrophs

• They 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.

Multiple Choice questions on Monera

Enterobacteria 

• They 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

• They 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 

• They are long and have a coil-shaped cell.They have flagella at both ends.

• They are commonly aquatic and pathogens. For Ex- Treponema.

• Mycoplasma are smallest cell without cell wall and survive without oxygen. Mycoplasma are pathogen of both plant and animals.

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