Microscopy and Staining Techniques

Vocabulary flashcards based on lecture notes about microscopy and staining techniques.

Resolution

The ability to distinguish small objects close together.

Magnification

An enlarged image of an object.

Contrast

The difference in color intensity between an object and its background.

Compound microscope

Microscope where the image is formed from more than 2 lenses.

Condenser

Collects and directs lights in a bright-field microscope.

Refraction

Bending of light as it passes through an object that slows its speed.

Dark-field optics

Enable microbes to be visualized as halos of bright light against darkness. Light shines at an oblique angle. Only light scattered by the sample reaches objective.

Fluorescence microscopy

For specimens with added dye, or naturally photosynthetic microbes; Shows bright colored (fluorescent) image of the object, protein, or structure.

Fluorophores

Chemical compounds that absorb/emit light of specific wavelengths. Can be a dye or protein.

Electron Microscopy (EM)

Microscopy in which electrons are used instead of a light beam.

Specimen Staining

Adding a stain/dye to the microbe itself to Increase visibility, preserve sample, and highlight morphological features.

Fixation

Internal and external structures preserved in position.

Basic Dyes

Dyes with a positive charge that bind to negatively charged molecules (Nucleic Acid, Surface of Bacteria).

Acidic Dyes

Dyes with a negative charge and bind to positively charged molecules, used often for cellular structures or background.

Simple Stains

Color added to cells but not background.

Differential Staining

Stains one kind of cell but not another.

Gram Stain

Distinguishes bacteria based on cell-wall properties into two groups: Gram-positive (or) Gram-negative.

Peptidoglycan

Rigid structure that lies just outside the plasma membrane; composed of sugars/amino acids.

Iodine

Traps Crystal Violet in Gram + bacteria cell walls; Mordant used Gram Staining.