Chapter 2: How we see the Invisible World

Lens

A medium with a curved surface that refracts and refocuses light to produce an image

Antoine van Leeuwenhoek

He is credited with the first observation of microbes, including protists and bacteria, w/ simple microscopes he made, the "father of microbiology", he sent his observations to the Royal Society of London

Robert Hooke

He was the first to describe what we now call cells, author of Micrographia,

Zaccharias Jansen

He was the probable inventor of the compound microscope

Different frequencies of light have different refractive indices for a given material,

How can a prism separate white light into different colors?

It can be increased by shortening the wavelength, increasing the numerical aperture, or using stains

How can resolution on a microscope be increased?

Diffraction

Light waves can also interact with small objects or openings by bending or scattering,

Dispersion

Separation of colors, an example being a rainbow

Simple Microscopes

These have a single lens

Compound Microscopes

These have multiple lens

Acid-Fast Stain

This is used to distinguish acid-fast bacteria from non acid-fast cells; acid-fast are RED, non acid-fast are BLUE

Gram Stain

This is used to distinguish cells by cell wall type (gram-positive and gram-negative); gram-positive will stain purple/violet, gram-negative will stain pink

Endospore Stain

This is used to distinguish organisms with endospores from those without, it is used to study the endospore; endospores appear bluish-green, other structures appear pink to red, tested for Mycobacterium Tuberculosis

Flagella Stain

This is used to view and study flagella in bacteria that have them; flagella are visible if present

Electron Microscopy

This microscope focuses electrons on the specimen using magnets, these produce much greater magnification than light microscopy

Absorbance

This occurs when a material captures the energy of a light wave, an example is glow in the dark plastics,

Reflection

This occurs when a wave bounces off material, an example is a cloth reflecting it's color off to us but absorbs many other colors of light

Transmission

This occurs when a wave travels through material, an example of this is light through glass,

Refraction

This occurs when light waves change speed and direction as they pass from one medium to another

Scanning Probes Microscopy

This produces images of even greater magnification by measuring feedback from sharp probes that interact with the specimen

Galileo Galilei

Used a compound microscope to examine insect parts

Capsule Stain

Used to distinguish cells with capsules from those without; capsules appear clear or as halos if present

Brightfield, Darkfield, Phase contrast, Differential Interference Contrast, Fluorescence, Confocal, and Two-Photon Microscopes

What are commonly used light microscopes?

Fluorescence Microscopy

What are fluorochromes used for?

Gram staining, acid-fast staining, capsule staining, endospore staining, and flagella staining

What are the common staining techniques?

TEM and SEM

What are two common forms of Electron Microscopy?

STM and AFM

What are two examples of Probe Microscopes?

Sputter-Coating

What do samples for SEM require?

Very thin sections

What do samples for TEM require?

Light with the shortest wavelength

What has a high energy?

Infrared rays

What has the lowest energy on the spectrum?

Ocular Magnification x Objective Magnification

What is magnification?

Safranin

What is the counterstain that allows dye adherance to gram-negative cells?

Alcohol

What is the decolorizer that washes away stain from gram-negative cell walls?

Violet

What is the highest frequency on the visible light spectrum?

Red

What is the lowest frequency on the visible light spectrum?

Iodine

What is the mordant that makes dye less soluble so it adheres to cell walls?

The Brightfield Microscope

What is the most common used microscope in microbiology?

Crystal Violet

What is the primary stain added to the specimen smear in gram-staining?

The Electromagnetic Spectrum

What is visible light apart of?

Fluorescent dyes and Phosphorescent Materials

Which materials can effectively transform nonvisible electromagnetic radiation into visible light?