![]() ![]() When used as an antibiotic treatment, penicillin operates by a very specific mechanism. Penicillin was first used to treat bacterial infections in 1942 and is derived from the fungus Penicillium sp. This teaching activity uses a step-wise process to aid the student in familiarity with the use of the microscope as well as to increase the success rate with which they are able to stain and view microorganisms.Modern physicians frequently prescribe antibiotic medications to help people fight infections. One of the first antibiotics discovered was penicillin. Core Microscopy Skills: Instructional Scaffolding for the Gram Stain.If the bacteria is Gram negative, it will lose the primary stain and take the secondary stain, causing it to appear red when viewed under a microscope. If the bacteria is Gram positive, it will retain the primary stain (crystal violet) and not take the secondary stain (safranin), causing it to look violet/purple under a microscope. Wash with a gentle stream of water for a maximum of 5 seconds. Add the secondary stain, safranin, to the slide and incubate for 1 minute.However, if the alcohol remains on the sample for too long, it may also decolorize Gram positive cells. The alcohol will decolorize the sample if it is Gram negative, removing the crystal violet. Rinse sample/slide with acetone or alcohol for ~3 seconds and rinse with a gentle stream of water.Add Gram's iodine for 1 minute- this is a mordant, or an agent that fixes the crystal violet to the bacterial cell wall.Rinse slide with a gentle stream of water for a maximum of 5 seconds to remove unbound crystal violet. ![]()
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