Introduction to the Microbial Nutrition

Introduction to the Microbial Nutrition

  • Microbial cells carry out several functions, which include metabolic processes and growth.
  • For these processes, energy sources are required, which are obtained by nutrients.
  • Nutrients are those substances that are energy sources to drive the metabolic or biosynthetic processes by the microbial cells.
  • Microbial nutrition are classified into two types based on the requirements.Nutritional requirement by microbes
  • The microbial cell is composed of some major elements such as Carbon, Oxygen, Hydrogen, Phosphorous, Sulfur, Potassium, iron, magnesium, and calcium. These are known as macronutrients or macroelements.
    • They are needed by microbial cells in large amounts.
  • For biosynthesis of macromolecules such as carbohydrates, proteins, nucleic acids, etc, macroelements (C, H, O, S, and N ) are required.
  • Other macroelements such as K, Fe acts as a cation or participate in other several roles in microbial cells.
  • Microelements such as Zinc, Cobalt, Magnesium, Copper, Nickel, and Molybdenum, are needed in small amounts.
    • They are also called trace elements.
    • Microelements are part of cofactors & enzymes and act as catalysts in the reactions carried within the cell.
    • For e.g., Zn is available at the enzyme’s active sites.

Nutrition required by the microbes

  • Microorganisms need macro elements (C, H &O) and electron sources.
    • Carbon, Hydrogen & Oxygen molecules are components of organic molecules.
    • Electron sources are used for other cellular works and also drive redox reactions.
    • Nitrogen is involved in the biosynthesis of the amino acids, nitrogenous bases i.e., purines & pyrimidines, etc.
    • Phosphorous is there in phospholipids, nucleic acids.
    • Sulfur is necessary for the biosynthesis of amino acids like cysteine & methionine, and other cofactors such as thiamine & biotin.

Overview of Sources of Carbon, Energy & Electron

Overview of Types of microorganisms on the basis of source of carbon, energy & electron

Broad classification of types of microorganisms based on nutritional requirements

  • Usually, microorganisms require all three sources i.e., carbon, energy, and electron sources,
  • As there are a diversity of microorganisms present in our environments, their nutritional requirements also vary.

Based on the  nutritional type it is broadly classified into five classes :

Nutritional Type Carbon Source Energy Source Electron Source E.g of Microorganisms
Photolithoautotrophy CO2 Light Inorganic e donors cyanobacteria, Purple & green sulfur bacteria,
Photoorganoheterotrophy Organic carbon or maybe CO2 Light Organic e donor Purple & Green non-sulfur bacteria
Chemolithoautotrophy CO2 Inorganic chemicals Inorganic e donors Iron-oxidizing
bacteria, methanogens, Sulfur-oxidizing bacteria, nitrifying


Organic carbon or maybe CO2 Inorganic chemicals Inorganic e donors Few sulphur-oxidizing bacteria e.g., Beggiatoa
Chemoorganoheterotrophy Organic carbon Organic chemicals Organic e donor Non-photosynthetic microbes
A. ) Cyanobacteria - Photolithoautotroph B.) Nitrobacter- Chemolithoautotroph
A. ) Cyanobacteria – Photolithoautotroph                              B.) Nitrobacter- Chemolithoautotroph
C.) Purple Sulfur Bacteria - Photoheterotrophs D.) Beggiatoa alba- Chemolithoheterotroph
C.) Purple Sulfur Bacteria – Photoheterotrophs                                D.) Beggiatoa alba– Chemolithoheterotroph
  • Some organic compounds are important for microbial growth but cannot be synthesized by few microbes, they are known as growth factors.
  • Generally, they are obtained from precursors present in the environments.
  • The types of growth factors are Vitamins, amino acids,  purines & pyrimidines.
  • On the other hand, microbes that are capable of producing vitamins are exploited for commercial use. For e.g., Riboflavin is produced by Candida, Ashbya, Clostridium.

References and Sources


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