Chapter 2: How We See the Invisible World – Microscopy

Vocabulary flashcards covering key microscopy concepts from Chapter 2 notes.

A method using lenses to magnify small objects; essential tool for microbiologists to study microbes.

Microscopy

Distance between successive crests of a wave; shorter wavelengths yield higher resolution in microscopy.

Wavelength

Ability to distinguish two close objects as separate; higher resolution means finer detail.

Resolution

How much a substance slows light; higher ____ can increase resolution when using appropriate optics.

Refractive index

ability of a sense to enlarge the image of an object when compared to the real object

Magnification

Oil used with high-power objectives (100X) to reduce light refraction and increase numerical aperture, improving resolution.

Immersion oil

Product of the ocular and objective magnifications

Total magnification

physical/chemical process that preserves specimens and adheres cells to slides before staining.

Fixation

Colored chemical used to visualize cells

Stain (dye)

Molecule that becomes a colored chromophore under staining conditions.

Chromogen

A charged group on a dye that helps it bind to the specimen and influence staining

Auxochrome

Medium in which a dye is dissolved to carry it into the specimen.

Solvent (staining)

A staining method using a single dye; all organisms appear the same color (typically purple)

Simple staining

Staining using multiple dyes to differentiate organisms; Gram staining is a key example.

Differential staining

Differential stain that distinguishes Gram-positive (purple) from Gram-negative (pink/red) bacteria.

Gram staining

Retains crystal violet and appears purple after safranin counterstain.

Gram-positive

Loses crystal violet and appears red/pink after safranin counterstain.

Gram-negative

Stains endospores (often green) inside bacterial cells to visualize their presence.

Endospore staining

Stains capsules around cells to visualize polysaccharide capsules.

Capsule staining

Stains flagella to visualize these slender locomotor structures.

Flagella staining

Bright-field, dark-field, phase-contrast, fluorescence, and confocal microscopes—each enhances contrast or specificity.

Light microscopy types

Light microscope with a bright background; image formed by transmitted light.

Bright-field microscopy

Illuminates specimens so only scattered light is captured; image on a dark background; good for live cells.

Dark-field microscopy

Uses refractive index differences and interference to produce high-contrast images of living cells.

Phase-contrast microscopy

Uses fluorescent dyes to visualize specific structures or molecules; enables pathogen ID and localization.

Fluorescence microscopy

Uses lasers to scan planes and build 3D images of thick specimens.

Confocal microscopy

Electrons replace light as the illuminating beam; much shorter wavelength yields higher resolution; reveals fine details.

Electron microscopy

Reveals internal ultrastructure by transmitting electrons through a thin specimen

TEM (Transmission Electron Microscope)

Reveals surface topography by scanning the specimen with electrons and detecting surface signals.

SEM (Scanning Electron Microscope)

highest point of a wave above the rest position (equilibrium)

crest

number of complete wave cycles that pass a given point in one second

frequency

when light waves strike a surface and bounce back instead of passing through

reflection

bending of light as it passes between media with different indices (air to glass)

refraction

combination of overlapping light waves that can reinforce or cancel each other

interference

separating or bending of light waves when they encounter edges, slits, or fine structures

diffraction

imparts color (stain)

chromophore