A selective medium is a substance (usually agar-based) which grows a specific type of microbe. Using different nutrient ratios, chemical compounds (e.g. methylene blue) and incubation times, speciation of bacteria can be performed before to use other methods for the presuntive identification of bacteria or fungus.
Some examples of selective media are:
Eosin-methylen blue agar (EMB) that contains methylene blue which is toxic for Gram-positive bacteria allowing only the growth (thus selecting) of Gram negative bacteria.
YM (Yeast and Mold) which has a low pH, deterring bacterial growth.
Blood agar (used in strep tests), which contains beef heart blood which becomes transparent in the presence of hemolytic Streptococcus.
The differential medium is one, which enables one to differentiate two types of organisms by their characteristic growth.
Selectivemedium is one that contains ingredients that affronter advantage to particular organism over others by all growth of the particular organism and inhibiting the others.
Enrichment medium is a liquid medina, which enema cues dm elm with of certain bacterial species, while show(ongoing the lag phase of tm~ ~gainers thus altering the rat two in favors of the required bacterial species.
When agar, a substance which sets into a gel, is added to a liquid medium it can be poured into petri dishes where it will solidify, called agar plates, and provide a solid medium on which microbes may be cultured.
Selective media are used to grow cells which possess a desired selectable trait.
While selective media are used to allow the growth of only select microoganisms, differential media allow the growth of multiple types, but result in distinguishing characteristics (such as the production of a brightly coloured or phosphorescent dye).
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