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.
Read: What is Stock Culture
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 |
Read: What is Fermentation
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.
| Composition | Gms/Litre |
|---|---|
| Yeast Extract | 6 |
| Peptic Digest of Animal Tissue | 40 |
| Dipotassium phosphate | 3 |
| Agar | 15 |
| Distilled Water | 1000 ml |
| pH | 7.0 ± 0.2 |
Read: What is Bioreactor
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 |
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Advantages of Enrichment Culture :
- Enrichment culture is an isolation technique designed for the growth and Development of particular microorganisms by providing favorable Nutrients and Environment.
- Enrichment culture techniques are used to increase the small number of organisms to a high number of molecules.
- 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.
- The advantages of Enrichment culture are it provides natural conditions,
- Enrichment culture is easy to replace without changing the container,
- Easy to sterilize with ultra-filtration.
- 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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