5. Cell Culture

Cell Culture Media

Blood agar plates are often used to diagnose infection. On the right is a positive Streptococcus culture; on the left is a positive Staphylococcus culture.

In cell culture techniques, cells (or tissues) are removed from a plant or an animal and introduced into a new, artificial environment that can support their proliferation (survival and growth).

Some of the requirements of such an environment for the proliferation of the cells include:

  • A substrate (source of nutrition)
  • Ideal temperature range (controlled)
  • Growth medium, and
  • Ideal pH among others

Here, we shall focus on the medium (cell culture media)

Although there are different types of culture media (for different types of cells) they are typically composed of:

  • Glucose
  • Amino acids
  • Vitamins
  • Inorganic salts
  • Attachment factors Etc.

There are two major types of culture media. These include:

Natural media – Natural culture media is composed of biological fluids that are naturally occurring. Although this type of media can be used for a range of cells, its biggest disadvantage is that it may lack the exact components required by given cells, which can greatly affect reproducibility.

Artificial media – Also referred to as synthetic media, artificial media refers to the type of media that is produced by adding such nutrients as vitamins, gases (oxygen and carbon dioxide) and protein among others. These organic and inorganic nutrients are added so as to meet the specific needs of given cells, and thus provide the ideal environment for their growth.

As such, they can be used for a number of purposes including:

  • Providing immediate survival of the cells
  • Allowing for prolonged survival of the cells
  • Allowing for indefinite growth of the cells
  • Providing for specialized functions

On the other hand, culture may be categorized as:

Selective media– This is a special type of media that only allows for certain cells to grow. For instance, blood agar (used to isolate Streptococcus & Moraxella species) can be turned in to a selective media by adding antibiotics.

Differential media– This type of media allows for different types of cells/microorganisms to grow depending on their metabolism.

As mentioned above, different types of synthetic media are prepared in a manner that will provide the ideal proliferation environment for given cells. For this reason, synthetic media can be divided in to four major categories.

These include:

Serum containing media – In these types of media, serum (fetal bovine serum) is used as a carrier for nutrients and growth factors among others that tend to be water insoluble.

Serum-free media – These types of media is typically produced for the purposes of supporting single cell type of culture. As such, it provides specified nutrients and other factors required by the cell type. In this media, serum is absent because it present some disadvantages and can result in misinterpretation of immunological results.

Chemically defined media – Like the name suggests, this type of media is composed of contamination- free pure organic and inorganic ingredients. Constituents of this type of media are typically produced through genetic engineering in bacteria/yeast.

Protein-free media – Protein- free media are typically lacking of any type of protein. It’s largely used to promote superior growth of the cells as well as protein expression in addition to facilitating for the purification of any expressed product.

Some of the major components of cell culture media include:

  • Nutrients – provided for by peptides and amino-acids, which are the building blocks of proteins
  • Carbohydrates for energy
  • Essential minerals  such as calcium, magnesium, phosphates and iron among others buffering agents such s acetates to stabilize the culture media
  • Vitamins
  • PH change indicators such as phenol red

Cell culture media are used for the proliferation of cells, which can then be identified and studied. As such, it can be used for various purposes including for education, diagnosis and treatment of a disease among others.

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