MCB 100 1st Edition Lecture 11 Outline of Last Lecture I. Magnification II. Resolution III. The limits of resolution with light microscopy IV. Electron microscopesV. Microscopy techniques A. Bright-field microscopyB. Dark-field microscopyC. Phase contract microscopy D. Fluorescent microscopy E. Electron microscopy Outline of Current Lecture I. Stains for Microscopy A. Simple stains B. Negative stains C. Differential stains i. The Gram stain ii. Schaeffer-Fulton Endospore Stain Current LectureI. Stains for MicroscopyA. Simple stains: basic dyes are used to stain the microorganisms. The chromaphore hasa positive change and binds to negatively charged groups on the bacterial cell wall. i. Used to stain microorganisms a bright color to make them more visible in Bright-Field Microscopy ii. Dyes used for simple stains are called basic dyes or cationic dyes (ex. Crystal violet, safranin, methylene blue) B. Negative stains: acidic dyes are used to stain the area around the microorganism. The chromaphore has a negative charge and sticks to glass.i. Negative stain is a procedure that is used to visualize the bacterial capsule. A capsule is a slimy layer of polysaccharides that coats the outside surface of some bacteria and protects the bacterium from the host immune system B. Differential stains: two or more dyes are used and different microorganisms stain different colors. This is caused by differences in the structure or chemical make-up ofthe cell surface of the microorganisms. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Ex. Gram stain, schaeffer-Fulton Endospore Stain, Ziehl-Neelsen Acid-Fast Stain ii. The Gram Stain: used to divide bacteria into 2 groups based on the thickness ofthe cell wall 1. Bacteria with thick cell walls will appear purple and are called gram positive2. Bacteria with thin cell walls will appear pink and are called gram positive ii. Schaeffer-Fulton Endospore Stain: used to identify spore forming bacteria in the Gram positive genera Bacillus and Clostridium 1. The endospore cell wall is mineralized with dipicolinic acid and calcium. 2. Endospore can be stained by the dye Malachite Green. Most bacteria don’t stain well with malachite Green. The red dye Safranin is used as a counterstain to see the vegetative (non-spore)
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