Kingdom Monera

• @@Bacteria@@ are the sole members of the Kingdom Monera.

  • They are the %%most abundant microorganisms.%%
  • Bacteria occur almost everywhere.

• Hundreds of bacteria are present in a handful of soil.

  • They also occur in extreme habitats such as hot springs, deserts, snow, and deep oceans where very few other life forms can survive.

• Bacteria as a group show the %%most extensive metabolic diversity.%%

  • Bacteria are grouped under four categories based on their shape:
  • Coccus: spherical
  • Bacillus: rod-shaped
  • Vibrio: comma shaped
  • Spirillum: spiral.

  

Some of the bacteria are:

• Autotrophic, i.e., they synthesize their own food from inorganic substrates. They may be photosynthetic autotrophic or chemosynthetic autotrophic.
• Heterotrophic, i.e., they depend on other organisms or on dead organic matter for food.

Archaebacteria:

• They live in some of the harshest habitats such as extreme salty areas (halophiles), hot springs (thermoacidophiles), and marshy areas (methanogens).
• They differ from other bacteria in having a different cell wall structure which helps them to survive in extreme conditions.
  • Methanogens are present in the ^^gut of several ruminant animals^^ such as cows and buffaloes
• These are responsible for the ==production of methane== (biogas) from the dung of these animals.

Eubacteria:

• They are also referred to as %%‘true bacteria’.%%
  • They are characterized by the presence of a rigid cell wall, and if motile, a flagellum.

Photosynthetic Autotrophs:

The @@cyanobacteria@@ (also referred to as blue-green algae) have chlorophyll similar to green plants and are @@photosynthetic autotrophs.@@

• The cyanobacteria are %%unicellular, colonial, or filamentous, and freshwater/marine or terrestrial algae.%%
  • The colonies are generally surrounded by a @@gelatinous sheath@@@@.@@
  • They often form a bloom in %%polluted water bodies%%%%.%%
  • @@Some of these organisms can fix atmospheric nitrogen in specialized cells called heterocysts.@@
• Examples: Anabaena and Nostoc.

Chemosynthetic Autotrophs:

• These bacteria oxidize various inorganic substances such as nitrates, nitrites, and ammonia and use the released energy for their %%ATP production.%%
  • They play a great role in ==recycling nutrients== like nitrogen, phosphorous, iron, and sulfur.

Heterotrophic Bacteria:

• The majority of these are important decomposers.

• They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legumes, etc.

  

• Some are pathogens causing damage to human beings, crops, farm animals, and pets.

  • Cholera, typhoid, tetanus, and citrus canker are well-known diseases caused by different bacteria.

Mycoplasm:

• These are organisms that completely %%lack a cell wall.%%
  • They are the ==smallest living cells== known and ==can survive without oxygen (anaerobic).==
  • Many mycoplasmas are pathogenic in animals and plants.

Reproduction:

• Bacteria reproduce mainly by fission.
  • Sometimes, under @@unfavorable@@ conditions, they produce @@spores.@@
  • They also reproduce by a sort of sexual reproduction by ^^adopting a primitive type of DNA transfer from one bacterium to the other.^^

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