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1GCC BIO205–Lab 5–Dr. AlvarezDifferential and Selective MediaLearning Objectives:Culture bacteria in different selective and differential mediaUse specialized media for the selection and differentiation of unknown bacteriaDiscuss the differences between differential, selective, and enriched mediaMaterials:Stock Culture:TSA slant ofEscherichia coli,Enterobacter aerogenes, Micrococcusluteus,andStaphylococcus epidermidis.Equipment:Inoculating loopbacticineratorMediaMacConkeyMannitol Salt Agar (MSA)Eosin-methylene blue agar (EMB)Phenyl ethyl alcohol (PEA)Discussion:Numerous different types of media are available for functions such as:•Isolation of bacterial types from a mixed population of organisms•Differentiation among closely related groups of bacteria according to theirmacroscopic appearance (characteristics of colonies) and biochemical reactions inthe medium.•Identify potential contaminant bacteria in water, sewage, or food.Media can be classified in selective, differential, and enriched. Some media are acombination of two of them. For example, Mannitol Salt Agar medium is selective ANDdifferentialA) Selective mediaThese media are used to select (isolate) specific group of bacteria but kill other groups ofbacteria. They contain chemical substances that block the growth of one type of bacteriawhile allowing growth of another.Example:Phenyl ethyl alcohol agar (PEA):This medium is used for the isolation of Gram-positivebacteria. The phenylethyl alcohol inhibit the growth of Gram-negative bacteria. Therefore,this medium is selective for Gram-positive bacteria and kills Gram-negative bacteria.
2B) Differential mediaThese media candistinguish between morphologically and biochemically related groupsof organisms. They contain chemical compounds that after bacteria grow, they will produce