Exam 1 Flashcards
1
Q
Light Microscope Parts
A
2
Q
Calculation of Total Magnification
A
Total magnification of the final image is a product of the separate magnifying powers of the two lens.
objective power x ocular power = total magnification
3
Q
Bacterial Shapes
A
4
Q
Bacterial Arrangements
A
- Arrangement of cells is dependent on pattern of division and how cells remain attached after division:
- Cocci:
- Singles
- Diplococci – in pairs
- Tetrads – groups of four
- Irregular clusters
- Chains
- Cubical packets (sarcina)
- Bacilli:
- Diplobacilli
- Chains
- Palisades
- Cocci:
5
Q
Simple Stain
Acidic Dyes
A
- net negative charge
- bind to components of cells and tissues that are positively charged.
- Surface of bacterial cells are negatively charged (due to Teichoic acid)
- basic dyes are most commonly used in bacteriology.
- Examples:
- Crystal Violet
- Methylene Blue
- Safranin
- basic Fuchsin
6
Q
Use for Simple Stain
A
7
Q
Negative Stain
A
- uses negative or acidic stains that do not bind to the test specimen
- observe a clear specimen against a dark coloured background
8
Q
Use for Negative Stain
A
- determines the bacterial shape and arrangement.
- helps us to stain the organisms that are too sensitive to be heat fixed.
9
Q
Types of Stains
A
- Simple Stains
- Crystal violet
- Methylene blue
- Safranin
- Differential Stains
- Gram stain
- Acid-fast stain
- Endospore stain
- Histological stain
- Special Stains
- Negative (capsule) stain
- Flagellar stain
10
Q
Heat Fixation
A
- passing a slide of bacterial cells through a flame until the underside of the slide is warm to the touch.
11
Q
Inoculating loops sterilized
A
- passing it at an angle through the flame of a gas burner until the entire length of the wire becomes orange from the heat.
- all contaminants on the wire are incinerated.
- Never lay the loop down once it is sterilized
- or it may again become contaminated.
12
Q
Advantages of Simple Stains
A
- simple method where one stain or reagent is used.
- quick process.
- determining the bacterial shape, size, arrangement.
- difference between the living and the non-living structures.
- morphological characteristics of the bacteria.
13
Q
Disadvantages of Simple Stains
A
- It only gives limited information about the morphological characteristics only.
- It does not help in identifying the classification of bacteria.
14
Q
Advantages of Negative Stains
A
- Through negative staining, clear unstained cells are easily observable against the black coloured stained background.
- A negative staining method does not involve the heat-fixing of the specimen. As a result, the cell will not deform by the heat.
- It can also stain heat-sensitive microorganisms like Spirochetes, Yeasts etc.
- The negative staining technique also permits examining a transparent capsule around the cell wall of various microorganisms like Cryptococcus neoformans.
- It is quite an easy and rapid method that makes the use of a single acidic stain only.
15
Q
Disadvantages of Negative Stains
A
- Negative staining does not provide much information about the cell rather than the cell size, shape and arrangement.
- By using this technique, we cannot examine a particular strain or a type of organism.
17
Q
Pure Cultures Techniques
Streak Plate Method
A
21
Q
Simple Stains
A
23
Q
Gram Stain
A
- Way to identify type of infectious bacteria
- Treatment differs based on outcome
- Smear bacteria sample across glass slide
- Heat fix the bacteria to the slide
- Apply crystal violet to the bacteria
- Apply iodine to the bacteria
- Wash with alcohol (destaining)
- Apply safranin to the bacteria
- Results
- Gram positive = purple
- Gram negative = pink
