Enrichment Culture Technique - Definition, Composition, Advantages

Enrichment Culture: Definition, Composition, Advantages

  • Enrichment culture is a technique that helps to isolate and identify particular types of bacteria or other microorganisms present in a sample.

Definition of Enrichment Culture

  • Enrichment culture is a technique in microbiology where specific conditions are created with the help of a specific growth medium to encourage the growth of specific microorganisms over others. 
  • Enrichment culture is a technique that helps to isolate and identify particular types of bacteria or other microorganisms present in a sample.

What is Enrichment Culture?

  • Enrichment culture is referred to as it is a technique used to grow a particular group of microorganisms on an enrichment media.
  • The media used for the enrichment culture is the enrichment media.
  • The process of enrichment is usually done by the addition of various nutrients,  growth factors, and environmental conditions that only allow the growth of an organism of interest. 
  • These techniques are used for several organisms, Small to detectable levels.
  • For example, if you wish to isolate a bacterium that is a halophile (these bacteria grow at a high salt concentration), incubate the sample at that high salt concentration.  
  • Organisms that cannot tolerate that high salt concentration will die or simply fail to grow, while halophiles will grow and increase in number, over time becoming a large and larger proportion of the total bacterial population in the sample.  This is an example of enrichment culture by modifying the physical conditions of media.
  • Enrichment can also be carried out by modifying the nutrient content of the culture medium by adding specific types of nutrients and inhibitors.

History of Enrichment Culture

The microbiologist and virologist Martinus Beijerinck invented the enrichment culture, a fundamental method of studying microbes from the environment. Sergei Winogradsky also experimented on bacteria using different Enrichment cultures.

Media Use for Enrichment Culture 

  • Enrichment media refers to the liquid media that allows only the growth of a particular type of microorganism and inhibits the growth of unwanted bacteria by adding inhibitors. 
  • Generally Enrichment media are in liquid form, so it is also known as Enrichment Liquid Media/Culture.
  • To stop the growth of unwanted microorganisms various kinds of Inhibitors are usually added to enrichment media. Inhibitors such as antibiotics Penicillins,  Tetracyclines, dyes, chemicals, High pH, Temperature alteration, etc. 
  • Examples of Enrichment media include the Lowenstein Jensen medium, selenite F broth, tetrathionate broth, alkaline peptone water, pseudosel Agar, etc.
  • Media with a high salt concentration will be selected for halophiles.
  • Selenite broth is used to selectively isolate Salmonella species. 
  • Alkaline Peptone Water is used for the cultivation of vibrio.

Organism Medium Used Purpose
Escherichia coli Luria-Bertani (LB) broth  General enrichment
Salmonella typhimurium Selenite F broth Selective enrichment for Salmonella
Clostridium sporogenes Reinforced Clostridial Medium Enrichment for anaerobic bacteria
Staphylococcus aureus Mannitol Salt Agar Selective enrichment for Staphylococcus
Listeria monocytogenes Fraser broth Enrichment for Listeria
Vibrio cholerae Alkaline Peptone Water Enrichment for Vibrio

Composition  of Enrichment Media : 

  • Enrichment media contains the various kinds of nutrients that are required for the growth of a wide variety of organisms.
  • Enrichment Medium is a highly nutritive medium that contains peptone and yeast extract which serves as a source of carbons, nitrogen, amino acids, growth factors, vitamins, and Dipotassium phosphate buffer for the growth of bacteria. 
  • Agar is used as a solidifying agent.

Yeast Extract6
Peptic Digest of Animal Tissue40
Dipotassium phosphate3
Distilled Water1000 ml
pH7.0 ± 0.2

Enriched Culture Media Examples

Enrichment Culture Medium Example Organisms
Rappaport-Vassiliadis broth (RV) Salmonella spp.
Preston broth Campylobacter spp.
Fraser broth Listeria monocytogenes
Modified E. coli broth (mEC) Escherichia coli O157:H7
Cooked meat medium Clostridium botulinum
Alkaline Peptone Water Vibrio cholerae
Buffered charcoal yeast extract agar Legionella pneumophila
Selenite F broth Salmonella typhimurium
Tetrathionate broth Salmonella spp.
Thioglycollate broth Anaerobic bacteria

Image Source: Reddit.com

Advantages of Enrichment Culture  

  1. Enrichment culture is an isolation technique designed for the growth and Development of particular microorganisms by providing favorable Nutrients and Environment.
  2. Enrichment culture techniques are used to increase the small number of organisms to a high number of molecules.
  3. One of the most important advantages of enrichment culture media is that it increases the chance of isolation of particular bacteria from a mixed culture.
  4. The advantages of Enrichment culture are it provides natural conditions, 
  5. Enrichment culture is easy to replace without changing the container, 
  6. Easy to sterilize with ultra-filtration.
  7. Enrichment media are used for various purposes such as the propagation of a large number of organisms, fermentation studies, and various other Microbiological tests.

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