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Eosin Methylene Blue (EMB, also known as "Levine's formulation") is a selective stain for Gram-negative bacteria. EMB contains dyes that are toxic for Gram positive bacteria and bile salt which is toxic for Gram negative bacteria other than coliforms. EMB is the selective and differential medium for coliforms. It is a blend of two stains, eosin and methylene blue in the ratio of 6:1. A common application of this stain is in the preparation of EMB agar, a differential microbiological medium, which slightly inhibits the growth of Gram-positive bacteria and provides a color indicator distinguishing between organisms that ferment lactose (e.g., ''E. coli'') and those that do not (e.g., ''Salmonella'', ''Shigella'').〔(Biochemical Tests Explanation )〕 Organisms that ferment lactose display "nucleated colonies" -- colonies with dark centers.〔(Differential Media (Levine's Formulation) )〕 This medium is important in medical laboratories by distinguishing pathogenic microbes in a short period of time.〔Bachoon, Dave S., and Wendy A. Dustman. Microbiology Laboratory Manual. Ed. Michael Stranz. Mason, OH: Cengage Learning, 2008. Exercise 8, "Selective and Differential Media for Isolation" Print.〕 *Rapid lactose fermentation produces acids, which lower the pH. This encourages dye absorption by the colonies, which are now colored purple-black. *Lactose non-fermenters may increase the pH by deamination of proteins. This ensures that the dye is not absorbed. The colonies will be colorless. On EMB if ''''E. coli'''' is grown it will give a distinctive metallic green sheen (due to the metachromatic properties of the dyes, ''E. coli'' movement using flagella, and strong acid end-products of fermentation). Some species of ''Citrobacter'' and ''Enterobacter'' will also react this way to EMB.〔(EMB Agar Growth Examples )〕 This medium has been specifically designed to discourage the growth of gram positive bacteria.〔()〕 EMB contains the following ingredients: peptone, Lactose, Dipotassium phosphate, Eosin Y (dye), Methylene blue (dye), Agar. There are also EMB agars that do not contain lactose. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eosin methylene blue」の詳細全文を読む スポンサード リンク
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