Lecture 2: Microscopy

Question 1

Resolution

Answer 1

distinguish 2 adjacent objects

Question 2

contrast

Answer 2

difference in brightness of structure

Question 3

brightfield microscope

Answer 3

dark image on light background
- stained

Question 4

darkfield microscope

Answer 4

bright image on dark background
- observe motility
- better resolution than brightfield
- unstained

Question 5

phase contrast microscope

Answer 5

objects have white glow & annular ring

Question 6

Differential Interference Contrast (DIC)

Answer 6

polarized light spilt into 2 beams
- unstained

Question 7

Fluorescence microscope

Answer 7

uses fluorochromes to emit light when excited
- attach to antibodies, lectins & DNA

Question 8

Confocal microscope

Answer 8

scans different layers

Question 9

Transmission electron microscopy (TEM)

Answer 9

electrons go through the sample
- best for internal structures (X section)

Question 10

Scanning electron microscopy (SEM)

Answer 10

image of the surface
- 3D like appearance

Question 11

What does a gram stain tell us?

Answer 11

the type of bacteria

Question 12

what does an acid-fast stain do?

Answer 12

uses wax layer
used to identify mycobacterium tuberculosis

Question 13

what is basic staining?

Answer 13

crystal violet & negative charged molecules

Question 14

what is acid staining?

Answer 14

rose bengal & positive charged molecules

Question 15

what is negative staining?

Answer 15

nigrosine & stains background NOT bacteria

Question 16

what can be used to improve resolution?

Answer 16

use oil to scatter cells

Question 17

what are the 3 staining steps?

Answer 17

1. prepare a culture smear
2. heat smear & add stain
3. add oil & uses 100x lens

Question 18

what are the 4 gram stain steps?

Answer 18

1. stain cells purple
2. add iodine
3. use alcohol to remove colour
4. counterstain with safranin

Question 19

gram positive characteristics

Answer 19

purple & thick
-no outer membrane

Question 20

gram negative characteristics

Answer 20

pink & thin
- has outer membrane

Question 21

what does endospore staining do?

Answer 21

uses 2 stains & green indicates spores