Phenylethyl Alcohol Agar
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Exercise 4-1: Phenylethyl Alcohol Agar Introduction: Selective media is media that encourage growth of some organisms and discourages growth of others. Phenylethyl Alcohol Agar is an undefined, selective medium that encourages growth of Gram-positive organisms and inhibits growth of most Gram-negative organisms. Sodium chloride is added to the medium to provide a stable osmotic environment and digests of casein and soybean are added for nutrition. PEA is selective against Gram-negative organisms because it breaks down their membrane barrier, which than allows substances that are usually blocked to leak into the cell while also causing leakage of a large amount of cellular potassium. Because of this, DNA synthesis is halted and ultimately disrupted. PEA is important because it helps isolate staphylococci and streptococci specimens, including enterococci and lactococci, when given a mixture of bacteria. In the end, the PEA plate is compared with the nutrient agar plate to determine how well specific micro-organisms grew on both plates. Results: Refer To Data Sheet.Discussion: From my results I obtained that Escherichia coli had poor growth in the PEA plate and because the PEA plate is a selective medium that encourages growth of Gram-positive bacteria and discourages growth of most Gram-negative bacteria I concluded that Escherichia coli was a gram-negative bacteria that was inhibited by the phenylethyl alcohol because it had better growth in the NA plate and very poor growth in the PEA plate. Using the website,
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