Lecture 2: Microscopy Flashcards
Resolution
distinguish 2 adjacent objects
contrast
difference in brightness of structure
brightfield microscope
dark image on light background
- stained
darkfield microscope
bright image on dark background
- observe motility
- better resolution than brightfield
- unstained
phase contrast microscope
objects have white glow & annular ring
Differential Interference Contrast (DIC)
polarized light spilt into 2 beams
- unstained
Fluorescence microscope
uses fluorochromes to emit light when excited
- attach to antibodies, lectins & DNA
Confocal microscope
scans different layers
Transmission electron microscopy (TEM)
electrons go through the sample
- best for internal structures (X section)
Scanning electron microscopy (SEM)
image of the surface
- 3D like appearance
What does a gram stain tell us?
the type of bacteria
what does an acid-fast stain do?
uses wax layer
used to identify mycobacterium tuberculosis
what is basic staining?
crystal violet & negative charged molecules
what is acid staining?
rose bengal & positive charged molecules
what is negative staining?
nigrosine & stains background NOT bacteria
what can be used to improve resolution?
use oil to scatter cells
what are the 3 staining steps?
- prepare a culture smear
- heat smear & add stain
- add oil & uses 100x lens
what are the 4 gram stain steps?
- stain cells purple
- add iodine
- use alcohol to remove colour
- counterstain with safranin
gram positive characteristics
purple & thick
-no outer membrane
gram negative characteristics
pink & thin
- has outer membrane
what does endospore staining do?
uses 2 stains & green indicates spores
