What is the difference between defined and undefined media

We use cookies to make your experience better. To comply with the new e-Privacy directive, we need to ask for your consent to set the cookies. Learn more. As a researcher working with microorganisms, you likely have varying needs for microbial cultivation.

When you grow microbes under controlled circumstances in the lab, you must provide a source of nutrients for their survival. These nutrients are contained in culture media. Many types of media are available, and which one you use depends on your intended purpose Table 1. The kinds and amounts of nutrients can vary, and other ingredients can be added to promote selective growth of desired microorganisms. Liquid broth and solid agar forms of culture media provide different growth environments for microbes, where the cells are either suspended in the broth or form colonies on the agar.

Broth media are used for the planktonic free-floating phase of microbial growth, and agar media are used for the isolated colony or large biofilm phase of microbial growth. However, biofilm studies can be conducted in broth as well, by allowing the biofilms to grow on the surface. You will likely use both broth and agar for different phases of an experiment or research application. Typically, organisms are initially grown in broth to reach a particular growth phase , at which point the cells can be plated on agar for further studies or long-term storage.

An undefined medium has some complex ingredients, such as yeast extract or casein hydrolysate, which consist of a mixture of many, many chemical species in unknown proportions. Undefined media are sometimes chosen based on price and sometimes by necessity — some microorganisms have never been cultured on defined media.

A defined medium also known as chemically defined medium or synthetic medium is a medium in which all the chemicals used are known, no yeast, animal, or plant tissue is present. A chemically defined medium is a growth medium suitable for the culture of microbes or animal cells including human of which all of the chemical components are known. A chemically defined medium is entirely free of animal-derived components including microbial derived components such as yeast extract and represents the purest and most consistent cell culture environment.

This is an important distinction between growth media types. A defined medium will have known quantities of all ingredients.

For microorganisms, it provides trace elements and vitamins required by the microbe and especially a defined carbon and nitrogen source. Glucose or glycerol are often used as carbon sources, and ammonium salts or nitrates as inorganic nitrogen sources. An undefined medium has some complex ingredients, such as yeast extract, which consists of a mixture of many, many chemical species in unknown proportions.

Undefined media are sometimes chosen based on price and sometimes by necessity — some microorganisms have never been cultured on defined media. There are many different types of media that can be used to grow specific microbes, and even promote certain cellular processes; such as wort, the medium which is the growth media for the yeast that makes beer.

Without wort in certain conditions, fermentation cannot occur and the beer will not contain alcohol or be carbonated bubbly. Nutrient media — A source of amino acids and nitrogen e.

On the other hand, complex media contain complex materials such as blood, milk, beef extract, yeast extract, etc. Overview and Key Difference 2. What is Chemically Defined Media 3. What is Complex Media 4. 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.