Kingdom Monera

KINGDOM MONERA

What are Monerans?

  • They are unicellular prokaryotic organisms found mostly in moist environments. 
  • These are the oldest known microorganisms on earth with no true nucleus.
  • They do not possess membrane-bound organelles and DNA is also not enclosed within the nucleus.

Characteristics of Kingdom Monera

  •  They lack nuclear membranes.
  •  They are devoid of plastids, mitochondria, and advanced (9+2 strand) flagella.
  •  They are typically unicellular organisms.
  •  The predominant mode of nutrition is absorptive but some groups are photosynthetic or chemosynthetic.
  •  Reproduction is primarily asexual by fission or budding.
  •  Protosexual phenomenon also occurs.
  •  Monera cells are microscopic.
  •  Most organisms bear a rigid cell wall which is made up of peptidoglycan.
  •  Examples- Anabaena, Nostoc, Oscillatoria, Bacteria.
  •  The kingdom Monera or Prokaryota is divided into two subkingdoms-Archaebacteria and Eubacteria.

 Prokaryotic cell

Bacteria

  •  Bacteria are the sole members of the kingdom Monera.
  •  They can survive in diverse environments.
  •  The bacteria are surrounded by two protective coverings- the outer cell wall and the inner cell membrane.
  •  Some bacteria are also covered by a capsule.
  • They exhibit autotrophic and heterotrophic modes of nutrition.

Bacterial Shape

  •  Cocci: They are oval or spherical in shape. These can be micrococcus (single), diplococcus (in pairs), tetra coccus (in fours), streptococcus (in chains), and staphylococcus (in clusters like grapes)
  •  Bacilli: They are rod-shaped. They may or may not have flagella.
  •  Vibrios: These are small and ‘comma or kidney’ like. They have a flagellum at one end and are also motile.
  • Spirillum: They are spiral or coiled like a cork­screw. The spiral forms are usually rigid and bear two or more flagella at one or both ends e.g., Spirillum, Spirochaetes, etc.
  • Filament: The body consists of small filaments like fungal mycelia. Examples include Beggiota, Thiothrix, etc.

                                Bacterial Shapes

Classification of Kingdom Monera

  • The kingdom Monera is divided into two subkingdoms-

1. Archaebacteria                    

2. Eubacteria

Archaebacteria

    •  Most Archaebacteria are autotrophs.
    •  Archaebacteria derive the energy they use for their metabolic activities from the oxidation of chemical energy sources, such as the reduced gases-ammonia (NH3), methane (CH4), or hydrogen sulfide (H2S).
    •  In the presence of one of these chemicals, Archaebacteria can manufacture their own amino acids and proteins.
  • Archaebacteria are divided into three groups-
  • Methanogens –
    •  According to their name, Methanogens manufacture methane as the result of their metabolic activities.
    •  Methanogens die in the presence of oxygen. Thus they are found in swamps and marshes in which all the oxygen has been consumed by the other organisms that live in these environments.
    • They are also present in the gut of cattle and termites.
  •  ThermoacidophilesThese Archaebacteria favor extremely hot and acidic environments, such as hot springs. Many Thermoacidophiles use hydrogen sulfide as their energy source.
  •  Halophiles-They survive in very salty environments, such as the Great Salt Lake and the Dead Sea which are extremely basic environments.

Eubacteria

  • They are also known as True bacteria.
  • They are found in all habitats (water soil, as well as on other organisms and so on.) all over the world.
  • They have rigid cell walls made up of peptidoglycan, which allows for the distinction between Gram-positive and Gram-negative bacteria.
  • They generally lack membrane-enclosed organelles such as nuclei, chloroplasts, and mitochondria.
  • Many bacteria are motile and contain one or more flagella.
  • Heterotrophs are organisms that obtain energy by consuming organic material.
  • They cannot produce their own food or organic material and therefore rely on organic material or food sources within their surroundings. Heterotrophic bacteria are plentiful in the natural world, with the majority of them functioning as decomposing agents.
  • Example of Eubacteria –
  •  Cyanobacteria-
    • These are also known as blue-green algae.
    • They are form of photosynthetic bacteria common in both marine and freshwater environments, deeply pigmented, causing blooms in polluted waters.
    • They contain chlorophyll, carotenoids, and phycobilins.
    • Some of these even fix atmospheric nitrogen.
    • Nostocs, Anabaena, and Spirulina are some cyanobacteria.

MYCOPLASMA

  • Mycoplasmas are the simplest known aerobic prokaryotic cell without a cell wall.
  • They are pleuropneumonia-like organisms (PPLO), discovered by Nocard and Roux (1898).
  • Nowak (1929) placed them in the genera Mycoplasma.
  • They were first isolated from bovine sheep suffering from pleuropneumonia.
  • Mycoplasma is considered to be intermediate between bacteria and viruses.