Difference Between Chemically Defined and Complex Media

The key difference between chemically defined and complex media is that the chemical defined media contain an exactly known chemical composition while complex media contain an unknown chemical composition.

When we grow microorganisms in laboratories, we must provide them with all the nutrients and conditions they need in order to obtain good growth. There are growth media or culture media for this purpose. The culture medium is a solid, semi-solid or liquid substrate that is rich in nutrients and other necessary elements and supports the growth of microorganisms. We carry out isolation, identification, and maintenance of microorganisms on culture media. There are different types of culture media depending on the composition and use. Chemically defined media and complex media are two main types of these. Chemically defined media contain pure biochemical; hence, the chemically defined media contain exactly known chemical composition. On the other hand, complex media contain complex materials such as blood, milk, beef extract, yeast extract, etc., so the chemical composition of the complex media is unknown.

CONTENTS

1. Overview and Key Difference
2. What is Chemically Defined Media
3. What is Complex Media
4. Similarities Between Chemically Defined and Complex Media
5. Side by Side Comparison – Chemically Defined vs Complex Media in Tabular Form
6. Summary

What are Chemically Defined Media?

Chemically defined media or synthetic media are a type of media that contains a known chemical composition. It is because this type of media contains pure chemicals or defined chemicals. Hence, the chemically defined media contain exactly known chemical composition. These media only provide the exact nutrients needed for the microbe for the growth. Therefore, prior to using this type of media, the researcher should know the exact nutritional requirement of the organism that he is going to cultivate in the medium.

Chemically defined media are useful when studying the minimal requirements of microorganisms and for a variety of physiological studies. Furthermore, these media are useful in in vitro cell cultures of human and animal cells. Glucose salt broth is one example of such media. Peptone broth is another example.

What are Complex Media?

Complex media are a type of media that contain complex materials which are of biological origin such as blood, milk, yeast extract, beef extract, etc. Hence, the chemical composition of complex media is unknown. Since complex media contains complex materials, they are rich in nutrients and provide a full range of growth factors. Thus, these media help to grow microorganisms that have complex nutritional requirements.

Furthermore, complex media are usually used for the cultivation of bacterial pathogens and other fastidious bacteria. Nutrient broth/agar, tryptic soy broth/agar, and blood agar are a few examples of complex media.

What are the Similarities Between Chemically Defined and Complex Media?

• Chemically defined media and complex media are two main types of culture media that allow the growth of microorganisms especially bacteria.
• They can be liquid, semi-solid or solid media.
• Also, both media contain nutrients and other growth factors for microbial growth.

What is the Difference Between Chemically Defined and Complex Media?

Chemically defined and complex media are the two main types of culture media. Chemically defined media have a known chemical composition while complex media have an unknown chemical composition. So, this is the key difference between chemically defined and complex media. Furthermore, the chemicals used for the preparation of the media are the reason behind known and unknown chemical compositions. We use pure biochemicals to prepare chemically defined media and complex materials such as blood, milk, beef extract, yeast extract to prepare complex media.

The following infographic provides more details on the difference between chemically defined and complex media comparatively.

Summary – Chemically Defined and Complex Media

 In summarizing the difference between chemically defined and complex media, the chemically defined media contain a known chemical composition, but complex media contain an unknown chemical composition. That is; the chemically defined media constitute pure chemicals/known chemicals while complex media constitute complex materials such as blood, milk, yeast extract, beef extract, etc. Therefore, this is the key difference between chemically defined and complex media. Furthermore, chemically defined media are minimal media that provide the exact nutritional requirements of organisms while complex media are rich cultures that provide a full range of nutrients and other growth factors for microorganisms.

Reference:

1. Todar, Kenneth, and Madison. Nutrition and Growth of Bacteria, Available here.
2.“Chemically Defined Medium.” Chemically Defined Medium – an Overview | ScienceDirect Topics, Available here.

Image Courtesy:

1. “Agar Plate” By Y tambe – Y tambe’s file (CC BY-SA 3.0) via Commons Wikimedia
2. “yy68 escherichia coli bap” By isis325 (CC BY 2.0) via Flickr