chapter 3 - microbes

Magnification

Increases the apparent size of an image

Resolution

Ability to distinguish details and provide clarity in an image

Micrometer

Unit commonly used for protozoa and bacteria; 10^-6 meters

Nanometer

Unit typically used for viruses; 10^-9 meters

Millimeter

Unit that some fungi and helminths can reach; 10^-3 meters

Light microscope (LM)

Microscope used with stained samples in the micrometer range

Fluorescence microscopy (FM)

Microscopy in which samples are stained with a fluorescent dye

Electron microscopy

Microscopy used for objects in the nanometer range

Scanning electron microscopy (SEM)

Electron microscopy that gives a 3D shape

Transmission electron microscopy (TEM)

A type of electron microscopy

Fixation and staining

Procedures that enhance detection and resolution of microbial cells

Fixation

Kills cells and stabilizes the sample on the slide

Stains

Bind to negative charges on the bacterial cell envelope and absorb visible light to add contrast

Differential stain

A stain that stains two different kinds of cells in a distinguishable manner

Gram stain

The most famous differential stain

Gram-positive cells

Cells that retain the Gram stain and appear dark purple

Gram-negative cells

Cells that are counterstained a different color and appear pink

Endospore stain

A differential staining method used to visualize endospores

Acid-fast stain

A differential staining method used for Mycobacterium tuberculosis

Flagella stain

A differential staining method used to visualize flagella such as peritrichous flagella

Protozoa

Microbes that are mostly in the micrometer size range

Bacteria

Microbes that are mostly in the micrometer size range

Viruses

Microbes that are typically in the nanometer size range

Fungi

Microbes that can reach the millimeter range

Helminths

Microbes that can reach the millimeter range and adult worms may be visible to the naked eye

Peritrichous flagella

Flagella visualized using a flagella stain