Lecture 2: Microscopy and Prokaryotic Cell Morphology Flashcards
What is the formula for magnification in microscopy?
(objective) x (eyepiece)
What is resolution in microscopy?
Ability of lens to distinguish between objects that are close together
What is the best resolution of a light microscope?
Human cells = 10-100 mm diameter, Bacteria = 1μm diameter
What size are viruses and can they be seen with light microscopes?
~0.01-0.1 μm, too small to see with light microscopes
What is a bright-field microscope?
Requires heat-fixing and staining, background appears light, bacteria color of stain
How does dark field microscopy differ from bright-field microscopy?
Background appears dark, organism appears bright due to light refraction
What is the principle behind phase contrast microscopy?
Converts slight differences in refractive indexes into variations in light intensity
What does fluorescent microscopy utilize to visualize specimens?
Uses UV light to excite fluorescent molecules
What do basic dyes and acidic dyes bind to?
Basic dyes bind negatively charged structures, acidic dyes bind positively charged structures
What is a simple stain?
1 stain is used to increase microbes visibility
What is a differential stain?
Divides microbes into different categories based on structural characteristics
What does the Gram stain identify?
Separates bacteria by the type of cell wall they have (+ or -)
Which bacteria are identified by acid-fast staining?
Bacteria with a thick waxy layer (mycolic acid) around them, e.g., Mycobacterium
What does endospore staining identify?
Identifies spore-producing bacteria with green endospores and pink cells
What are the shapes of bacteria classified as cocci?
Round, spherical
What are the arrangements of cocci?
- Diplococci * Streptococci * Staphylococci * Tetrads * Sarcina
What are bacilli?
Rod-shaped bacteria with different length to width ratios
What are the types of bacilli arrangements?
- Coccobacillus * Diplobacillus * Streptobacillus
What are vibrios?
Curved rods, comma-shaped
What are spirilla and spirochetes?
- Spirilla: corkscrew-shaped with flagella * Spirochetes: corkscrew-shaped without external flagella
Fill in the blank: The staining process requires microbes to be _______ to the slide.
fixed
True or False: Fluorescent microscopy can only visualize dead cells.
False
What is the resolution of electron microscopes compared to light microscopes?
1000X better than light microscope → 5x10-4 (.0005) μm resolution
