Classification of Bacteria on the Basis Of Nutrition and Its Types

Classification of Bacteria

Classification of Bacteria on the basis of nutrition. Bacteria are classified into two main group. One is autotrophic bacteria and other is heterotrophic.

Autotrophic Bacteria:

In this type those bacteria are included that can synthesis own food for our survival. They convert compound organic into simple inorganic substance. They obtain carbon from carbon dioxide to synthesis their food.

Autotrophic bacteria further classified into two group.

  1. Photoautotrophs
  2. Chemoautotrophs


  1. In which those bacteria are included that’s energy source are light.
  2. These bacteria have chlorophyll for photosynthesis.
  3. They can synthesis their own food.
  4. These bacteria chlorophyll same as plants chlorophyll, but in which chloroplast are absent.
  5. They use sunlight as an energy source and for hydrogen they use hydrogen sulphide instead of water.
  6. This process releases Sulphur as a byproduct.

Photoautotrophs further classified based on Hydrogen source;

  1. Purple Sulphur bacteria
  2. Green Sulphur bacteria
  3. Purple Non-Sulphur bacteria

Purple Sulphur bacteria:

These bacteria use Sulphur compound as source of proton and electron, e.g. chromatiumokenii.

Green Sulphur bacteria:

These bacteria use H2S as source of Proton and electron, e.g.  Chlorobacterium

Purple Non-Sulphur bacteria:

These bacteria use organic compound as source of electron and proton such as Rhodospirullummrubrum.


Chemoautotrophs are those bacteria that get energy from oxidation of inorganic substance during respiration.

  1. They maintain the soil fertility.
  2. They also play vital role in biosphere.
  3. They also perform nitrogen cycle.

Types of chemoautotrophs bacteria:

  • Iron bacteria
  • Sulphur bacteria
  • Hydrogen bacteria
  • Methane bacteria

Nitrifying Bacteria:

  1. They live in soil and oxidize ammonia gas in to nitrites, e.g. Nitrosomonas.
  2. Some bacteria convert nitrites into nitrates for plants e.g. Nitrobacter
  3. In this process energy is released and this energy used by bacteria.

Iron Bacteria:

  1. These bacteria present in iron rich in water.
  2. They oxidize ferrous compound into ferric and get energy from this process. E.g. Leptothrix, Ferrobacillus and Cladothrix.

2Fe (HCO3)2 + H2O   →  2Fe(OH)3 + 4CO2 + 29Kcal

4FeCO3 +O2 +6H2O   →  2Fe(OH)3 + 4CO2 + 81Kcal

Sulphur Bacteria:

  1. These bacteria found in hot springs that contain hydrogen sulphide.
  2. They oxidize metallic Sulphur to Sulphur and get energy. e.g. Thiothrix

Hydrogen Bacteria:

They grow in organic medium that consist of hydrogen, CO2 , O2 and oxidise hydrogen. e.g. Bacillus panctotrophus

Heterotrophic Bacteria:

This type of bacteria get energy from organic compound. They are not able to prepare their food. They depend on another organism. Classification of Bacteria Given Below.

Types of Heterotrophic Bacteria:

  1. Saprotrophic Bacteria
  2. Parasitic Bacteria
  3. Symbiotic Bacteria

Saprotrophic Bacteria:

  1. These bacteria get their energy from dead organic matter.
  2. They decompose the dead organic matter and get food and convert it into hums.
  3. These bacteria also known as decomposer.
  4. These bacteria secret decomposition enzyme that digest the complex organic matter in simple matter.
  5. These matters observed by bacteria as source of energy.

Parasitic Bacteria:

  1. These bacteria are also heterotrophic and not have any enzyme for decomposition.
  2. They total depend on another organism.
  3. They use the host enzyme to prepare their energy for growth.
  4. Most of these bacteria cause disease in host.
  5. These bacteria also called pathogens.
  6. Example Pneumococcus cause Pneumonia.

Symbiotic Bacteria:

  1. These bacteria act as symbiotic way with host and live together.
  2. They prepare food for host and in return get energy from host.
  3. Mostly these bacteria live in root of leguminous plants.
  4. They fix nitrogen for plants in the form of nodules. \

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