Microbial Nutrition and Metabolism

Microbial nutrition and metabolism

One of the characteristics of living organisms is their ability to grow. Just like plants and animals microorganisms also grow and they require nutrients to grow. These nutrients are required in either large quantities or small quantities. Nutrients are food substances that provide nourishment to help sustain an organism and the ability of an organism to assimilate these food substances and use them for growth is called Nutrition.

In this blog post we will be going through the various types of microbial nutrition, the types of nutrients available for microbial growth, the growth factors needed by microorganisms and a whole lot more!

So, What exactly is microbial nutrition?

Microbial nutrition

Microbial nutrition is the biochemical process of a microorganism to use food to support itself. You may be wondering how microorganisms feed since they are very little and do not have teeth for chewing food like higher animals. Well, microorganisms do not need to have teeth before they eat, these organisms ingest their food through their body parts. Some make use of their flagella to capture prey, some use their pseudopodia in engulfing their prey and those with cilia push their food into the mouth structure on their body parts.

Importance of Microbial Nutrition

Nutrition is important to these organisms because they get to replace all the nutrients they have lost.

Nutrition creates room for the growth of these microorganisms.

Nutritional Types of Microorganisms 

There are two types of microbial nutrition






Heterotrophs are organisms that are incapable of producing their own food. 


Autotrophs are organisms that can produce their own food using light, carbon dioxide, water or other chemical elements.


Chemotrophs are organisms that obtain energy through chemosynthesis.


Phototrophs are organisms that produce their food by using energy from sunlight to synthesize organic compounds.

What is nutrition without nutrients?

Microorganisms require two categories of nutrients for their growth and they are;



  • Macronutrients

Macronutrients are nutrients required by microorganisms in large quantities. These nutrients are essential for their growth and their life processes e.g metabolism. Nutrients that fall under this category are;

  • Carbon
  • Hydrogen
  • Nitrogen
  • Oxygen
  • Phosphorus
  • Sulphur 


Carbon is needed in very large quantities by microorganisms because it supplies their energy and it also helps these microorganisms break down carbohydrates.


Hydrogen is used as an electron donor by microorganisms.


Nitrogen also plays a very important role in microbial nutrition, its function is to synthesize amino acids and proteins in microorganisms.


Some microorganisms require oxygen to grow, these types of microorganisms are referred to as aerobic organisms. Oxygen also acts as the final electron acceptor for the electron transport chain.


Phosphorus is needed by microorganisms for the synthesis of genetic and cellular components.


Sulphur is used as an electron receptor during respiration.

  • Micronutrients

The word “micro” means small. So micronutrients as the name implies refers to nutrients that are needed in very small quantities by microorganisms. These nutrients are also not essential for the growth of these organisms. Micronutrients are also called trace elements. Nutrients under these category are 

  • Zinc
  • Cobalt
  • Molybdenum
  • Nickel 
  • Copper
  • Manganese 

Growth Factors

What are growth factors?

Growth factors are secreted biologically active molecules that can affect the growth of cells.

There are three growth factors needed by microorganisms and they are;

  • Vitamins
  • Nucleic Acids (purines and pyrimidines)
  • Amino Acids


Just like humans, microorganisms need vitamins. Most times vitamins act as coenzymes in these microorganisms and also supply them with what they need to be healthy.

Nucleic Acids (purines and pyrimidines): 

The growth factors, purines and pyrimidines are two families of nitrogenous bases that make up nucleic acids .

Many microorganisms can degrade purine and pyrimidine compounds to meet their carbon and nitrogen demands when their preferred substrates are exhausted.

Amino Acids:

Amino acids are very important for microorganisms because they support their growth and survival and also regulate energy and protein homeostasis in them.

Classifications of Microorganisms Based on Oxygen Requirements

There are so many classifications of microorganisms, but we’re going to discuss the classifications of these microorganisms based on their different needs for oxygen. 

Microorganisms use oxygen in their growth process but what you must know is that not all microorganisms use oxygen, there are some microorganisms that find it difficult to stay in an oxygenated environment because they rarely survive in such environment and these microorganisms are known as anaerobes which means “no-oxygen”.

Here are the different classes of microorganisms

1.Obligate aerobe

2.Obligate anaerobe

3.Facultative aerobe

4.Facultative anaerobe

5.Microerophilic organisms

Obligate Aerobes:

An obligate aerobe is a microorganism that lives only in the presence of oxygen. These microorganisms cannot make ATP in the absence of oxygen. Examples of microorganisms that fall in this category are; Bacillus, Mycobacterium tuberculosis, Nocardia asteroides and some fungi.

Obligate Anaerobes:

An obligate anaerobe is a microorganism that does not survive in the presence of oxygen but these microorganisms can survive without oxygen. Examples of obligate anaerobes are; Bacteroides fragilis, Clostridium perfringens and Clostridium tetani.

Facultative Aerobes:

A facultative aerobe is a microorganism that makes ATP by anaerobic respiration. Facultative Aerobes are also able to survive in both aerobic and anaerobic environments. 

Facultative Anaerobes:

Facultative anaerobes are microorganisms that grow in the presence and absence of oxygen. Examples of facultative anaerobes are; E.coli, Staphylococcus aureus and Staphylococcus epidermis .

Microaerophilic Organisms:

Microaerophilic organisms are microorganisms that grow best at reduced oxygen pressure. Examples of microaerophilic organisms are; Campylobacter coli, Campylobacter jejuni and Campylobacter lari.