Question

Research the categories of growth media listed below. Describe the use of each one. Name at least two media found in each category and the organisms that can grow on each. If a special reaction occurs in the media, please explain.

Growth media: Defined, Complex, Selective, Differential, Transfer.

Please write a text (not handwritten or cursive)

Answer 1

Defined growth media: A defined growth media contains known quantities of all ingredients. They consist of providing trace elements and vitamins especially defined carbon and nitrogen sources. The most common carbon sources used are glycerol or glucose. The most common nitrogen sources are ammonium salts or nitrates.

Complex media: A complex growth media contains some complex ingredients such as yeast extract or casein hydrolysate, which consist of a mixture of 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. For example Neisseria gonorrhoeae, which requires blood or hemoglobin and several amino acids and vitamins in order to grow.

Selective growth media: Selective growth media contains specific nutrients for the growth of only selected microorganisms. For example, if a microorganism is resistant to tetracycline, then tetracycline can be added to the medium to prevent other cells, which do not possess the resistance, from growing. For example buffered charcoal yeast extract agar is selective for certain Gram-negative bacteria, especially Legionella pneumophila, and baird–Parker agar is for Gram-positive staphylococci.

Differential growth media: Differential media used to differenciate one microorganism type from another growing on the same medium.This type of media uses the biochemical characteristics of a microorganism growing in the presence of specific nutrients or indicators (such as neutral red, phenol red) added to the medium to visibly indicate the defining characteristics of a microorganism. For example eosin methylene blue is differential for lactose fermentation, Granada medium is selective and differential for Streptococcus agalactiae.

Transfer growth media: Tranfer growth media contains only buffer and salt and used for the emporary storage of specimens being transported to the laboratory for cultivation. They Lack of carbon, nitrogen, and organic growth factors so as to prevent microbial multiplication. For example thioglycolate broth for strict anaerobes, and Venkataraman Ramakrishna (VR) medium is for V. cholerae