Ch. 2: How We See The Invisible World Flashcards
purpose of brightfield microscope
Used in wide variety of lab applications as standard microscope
Purpose of dark field microscope
- increases contrast w/out staining
- useful for viewing live specimens
Type of image produced by brightfield microscope
produces image on bright background
Example of bacteria visualized by brightfield microscope
Bacillus sp. showing endospores
Image produced by darkfield microscope
produce bright image on dark background
Example of bacteria visualized by darkfield microscope
Borrelia burgdorferi
Purpose of phase contrast microscope
- uses refraction & interference caused by structures in specimen to create high contrast, high res images w/out staining
- useful for viewing live specimens, structures such as endospore & organelles
Image produced by phase contrast microscope
uses refraction & interference caused by structures in specimen to create high contrast, high res images w/out staining
Example of bacteria visualized with phase contrast microscope
Pseudomonas sp.
Purpose of differential interference contrast (DIC) microscope
- uses interference patterns to enhance contrast between different features of a specimen
- useful in distinguishing structures within live, unstained specimen
Image produced by differential interference contrast (DIC) microscope
- high contrast image of living organisms with a 3D appearance
- images viewed reveal detailed structures within cells
Example of bacteria visualized by differential interference contrast (DIC) microscope
E. coli O157:H7
Purpose of fluorescence microscope
- uses fluorescent stains to produce an image
- can be used to identify pathogens, find particular species, distinguish from dead cells, find locations of particular molecules within a cell
Image produced by fluorescence microscope
Example of bacteria visualized by fluorescence microscope
P. putida stained with fluorescent dyes to visualize the capsule
Purpose of confocal microscope
- scan multiple z-planes successively
- useful for examining thick specimens such as biofilms
Image produced by confocal microscope
produce numerous 2D high res images at various depths that can be constructed into 3D image by a computer
Example of bacteria visualized by confocal microscope
E. coli stained with acridine orange due to show nucleoid region of cells
Purpose of two-photon microscope
- use scanning technique, fluorochromes, & long wavelength light
- penetrates deep into thick specimens such as biofilms
Image produced by two-photon microscope
Example of bacteria visualized by two-photon microscope
mouse intestine cells stained with fluorescent dyes
Purpose of transmission electron microscope (TEM)
- uses electron beams that pass through specimen to visualize small images
- useful to observe small, thin specimens such as tissue sections & subcellular structures
Image produced by transmission electron microscope (TEM)
Example of bacteria visualized by transmission electron microscope (TEM)
ebola virus
Purpose of scanning electron microscope (SEM)
- uses electron beam to visualize surfaces
- useful to observe 3D surface details of a specimen
Image produced by scanning electron microscope (SEM)
Example of bacteria visualized by scanning electron microscope (SEM)
Campylobactor jejuni
Purpose of scanning tunneling microscope (STM)
Image produced by scanning tunneling microscope (STM)
Example of bacteria visualized by scanning tunneling microscope (STM)
Purpose of atomic force microscope (AFM)
Image produced by atomic force microscope (AFM)
Example of bacteria visualized by atomic force microscope (AFM)
Basic stain examples
- methylene blue
- crystal violet
- malachite green
- basic fuchsin
- carbolfuchsin
- safranin
Basic stain purposes
stain negatively charged structures & molecules such as nucleic acids & proteins
Basic stain outcome
Positive stain
Acidic stain examples
- eosin
- acid fuchsin
- rose bengal
- congo red
Acidic stain purposes
stain positively charged molecules & structures such as proteins
Acidic stain outcome
Can be either positive or negative stain depending on cell’s chemistry
Negative stain examples
- india ink
- nigrosin
Negative stain purpose
stains background, not specimen
Negative stain outcome
Dark background with light specimen
Gram stain dyes
- crystal violet
- Gram’s iodine
- ethanol (decolorizer)
- safranin
Gram stain purpose
used to distinguish cells by cell-wall type (gram-negative, gram positive)
Gram stain outcome
- Gram-positive cells stain purple/violet
- Gram-negative cells stain pink
Acid-fast stain dyes
- after staining w/basic fuchsin, acid-fast abcteria resist decolorization by acid-alcohol
- non acid-fast bacteria are counterstained w/methylene blue
Acid-fast stain purpose
used to distinguish between acid-fast bacteria, such as M. tuberculosis, from non acid-fast cells
Acid-fast stain outcome
- acid-fast bacteria are red
- non acid-fast bacteria cells are blue
Endospore stain dyes
uses heat to stain endospores w/malachite green (Schaeffer-Fulton procedure), then cell is washed & counterstained w/safranin
Endospore stain purpose
- used to distinguish organisms w/endospores from those w/out
- used to study endospores
Endospore stain outcome
- endospores appear bluish-green
- other structures appear pink to red
Flagella stain dyes
flagella are coated w/a tannic acid or potassium alum mordant, then stained using either pararosaline or basic fuchsin
Flagella stain purpose
used to view & study flagella in bacteria that have them