Be able to identify the parts of the microscope!
ON POWERPOINT!
Smear
A smear is just a film of bacteria on a glass slide.
Heat Fixing
-Kills the bacteria
-Helps adhere the cells to the slide
Simple Stain
-Surfaces of microbes are negatively charged and attract the basic dyes that are positively charged
-Stains all the cells the same color
-Opposites attract
-Certain structured not stained by this method may be easily seen.
-Reveals shape, size, and arrang
Negative Stain
-Microbe repels dye, the dye stains the background, not the cell
-Acidic dye is negatively charged along with the cell
-Smear is not heat fixed
-Reveals shape, size, and arrangement
Differential Stain
-Use a primary stain and a counter stain to distinguish cell types or parts
-Helps distinguish between different kinds of bacteria
Examples: Gram stain, acid-fast stain, and endospore stain
Gram (+) Stain
�Gram (+) stains blue; these cells are typically simple and contain more peptidoglycan in the cell wall.
-Retain crystal-violet
Gram (-) Stain
�Gram (-) stains red; these cells are more complex, contain less peptidoglycan, and contain lipopolysaccharides (LPS).
-More likely to cause disease
-Lose crystal violet
Structural stains
-Reveal certain cell parts not revealed by conventional methods
-Capsules, endospores, and flagella
The Gram Stain
-Differential stain that distinguishes cells with a gram (+) cell wall from those with a gram (-) cell wall.
-Important basis of bacterial classification and identification
+Bacterial taxonomy
+Cell wall structure
-Practical aid in diagnosing infections
The four steps of the Gram Stain?
(1) crystal violet, (2) iodine, (3) alcohol de-colorizer, (4)safranin.
Chemical reaction in the cell for (+) and (-) Gram Stain?
Both cell walls stain with the crystal violet dye. However, the Gram (+) cells trap the crystal violet dye in the cells after iodine (mordant) application while there is no effect of iodine on the Gram (-) cells. Gram (+) crystals remain in the cell after
Bacteria Shapes: Cocci
Spheres
Bacteria Shapes: Bacilli
Short, fat rods
Bacteria Shapes: Spirilla
Spirals
Gram stain color and shape for: Bacillus sp.
-Gram (+) blue
-Bacilli-rod shaped
-Spore former
Gram stain color and shape for: E. coli
-Gram (-) red
-Bacilli- rod shaped
Gram stain color and shape for: Staphylococcus sp.
-Gram (+) blue
-Cocci- circular shaped