Mannitol salt agar is an example of _____. (Choose the answer the correctly completes the statement). O Selective media O Neutrogenic media O Differential media O Ionic growth media
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It selects for salt-tolerant organisms (like *Staphylococcus*) while differentiating between those that ferment mannitol (indicated by a color change) and those that do not. Show more…
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Growth media that can be changed through a functional effect specific microorganisms have on the media is defined as a Select one: selective media b. complex media defined media differential media
Suman K.
Introduction: Selective and differential media are used frequently in Microbiology Pathology Labs to identify a known group of bacteria from a complex mix of other bacteria. The medium is designed to select against as many of the background organisms as possible by using a medium in which they will not grow but the organisms under investigation can grow hence the ‐Selective‐ part of the name. Any assayable characteristic that can be used to differentiate a specific group of interest from the selected group of organisms can be incorporated into the medium to distinguish that group. The aim of this Lab is to understand use of selective/differential media and the interpretation of their results. Mannitol salt agar Contains: 7.5% NaCl included with the sugar mannitol, a source of protein, pH indicator (phenol red) Selection: The high salt concentration selects against salt intolerant organisms and for halophiles (salt tolerant organisms). Describe your results Eosin methylene agar Contains: EMB contains: peptone, lactose, dipotassium phosphate, eosin Y (dye), methylene blue (dye). Selection: Eosin and methylene blue together inhibit the growth of gram positive bacteria and encourage the growth of gram negative bacteria including coliforms Differentiation: Lactose is a fermentable carbohydrate that differentiates between organisms that ferment lactose (e.g., E. coli) and those that do not. In our plate Escherichia coli went through fermentation because it produced a metallic green sheen. The other samples produced pink colonies, which means they were slow or weak fermenters MacConkey agar: Contains: Protein source, lactose, bile salts, and the dyes crystal violet and neutral red. Selection: Bile salts and crystal violet make the medium selective by inhibiting the growth of gram-positive bacteria but allowing many gram negatives (including coliforms) to grow. Differentiation: Lactose is a fermentable carbohydrate that differentiates between organisms that ferment lactose (e.g., E. coli) and those like Pseudomonas and Klebsiellosis that do not. In our plates we did not yield any results because the plates were covered with a thin layer of MacConkey agar. Describe your results Triple sugar iron agar Contains: Carbon sources Three sugars, glucose (0.1%), sucrose (1%), and lactose (1%) and peptone as a source of protein.
Josee P.
Mannitol salts agar is a medium that contains a high concentration of salt (7.5%) and mannitol as a fermentable carbon source. Few organisms are able to grow on it because of its high salt concentration. Organisms that can grow and ferment mannitol will produce an acid that interacts with the pH indicator in the media, turning it yellow. Non-mannitol-fermenting organisms grow without any change to the media. Which of the following correctly describes this medium? a. selective and differential b. differential c. selective d. neither selective nor differential
Adi S.
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