Study GuideMicrobiology–Microscopy1.Staining TechniquesMicroorganisms are usuallycolorless and transparent, which makes them difficult to see under alight microscope. To make them visible and easier to study, scientists usestaining techniques.Stains add color to microbial cells or their surroundings, helping us observe size, shape, andstructure.1.1When Staining Is Not NeededIn some situations, staining is unnecessary. For example:•When microorganisms arevery large•Whenmotility (movement)needs to be observedIn these cases, awet mountis prepared. A drop of the microbial sample is placed directly on a slideand observed.Another method is thehanging drop technique, where:•A drop of culture is placed on a cover slip•The cover slip is inverted over a hollow slideThis method is especially useful for studying motility in living microorganisms.1.2Preparing a Smear for StainingBefore staining, the microorganisms must be prepared properly:1.A small amount of microbial sample is placed on a slide2.The sample is allowed toair dry3.The slide isheat fixedby passing it quickly through a flamePreview Mode
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