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?