The fecal sample was diluted and a small sample was used to inoculate an agar di
ID: 201882 • Letter: T
Question
The fecal sample was diluted and a small sample was used to inoculate an agar dish containing Hektoen agar. Hektoen agar has the following formula: 12.0gm 12.0gm 12.0gm 9.0gm 5.0gm 5.0gm 3.0gm 2.0gm 1.5gm 0.1gm 0.064gm 13.5gm Lactose, sucrose and salicin are all Çarbohydrate food sourçes. Sodium thiosulfate and Ferric Ammonium citrate cause the colonies to turn black if the bacteria is capable of producing H2S. Acid Fuschin and Bromothymol Blue cause the agar to change color if a change in pH occurs. Bile salts prevent the growth of Gram positive bacteria. Peptic Digest of Animal Tissue Lactose Sucrose Bile Salts Sodium Chloride Sodium Thiosulfate Yeast Extract Salicin Ferric Ammonium Citrate Acid Fuchsin Bromothymol Blue AgarExplanation / Answer
Answer 4:
A defined medium is a medium where the compositions of the medium are pure and well defined and the quantity is known. On the other hand, in an undefined medium, though the compositions of the medium are known, their individual quantity used will not be known. For example, Luria broth is an undefined medium as the yeast extract present in the medium has unequal proportions of chemical species.Thus, a medium cannot be both defined as well as undefined.
Answer 5:
Definition of differential medium (DM): A DM is a type of medium which helps in the identification and distinguishing of various organisms in the medium depending upon their growth kinetics/ characteristics. Organisms having different growth characteristics show visible differences in the differential medium.
Definition of selective medium (SM): SM allows the growth of a particular type of microorganisms and inhibits the growth of other types. These media may contain antimicrobials, dyes or other inhibitors which will aid only the growth of organism under study.
Some media may contain both DM as well as SM components in order to allow the growth of certain group of microbes and aid the investigator to visibly check the difference of growth pattern between the microbes present in the tool. This type of mixed medium is used as diagnostic tools.
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