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COLONY MORPHOLOGY ON AGAR PLATE CULTURES
Form of Colony
Elevation of Colony
Margin of Colony
Surface of Colony
MORPHOLOGY ON slant medium
•In a liquid medium, the region in which the organism grows depends on the oxygen
requirement of that particular species.
Liquid medium* Turbid
* Pellicle((thick growth at the top of the tube
* Sediment
There are
three common shapes of bacteria
1-Coccus
Diplococcus: a pair of cocci
having one of the following arrangements
Streptococcus: a chain of cocci
Tetrad: a square of 4 cocci
Sarcina: a cube of 8 cocci
Staphylococcus: cocci in irregular, often grape-like clusters
Bacillus (rod) 2-
Bacillus: a single bacillus
Streptobacillus: bacilli in chains
Coccobacillus: oval and similar to a coccus
Spiral 3-
Vibrio: an incomplete spiral or comma-shaped
Spirillum: a thick, rigid spiral
Spirochete: a thin, flexible spiral
Simple Stai
Simple Staining and Bacterial Cell Morphology
Preparing a smear for staining. (The following procedure is used for all of our staining)
•1. Flame (sterilize) your inoculating loop/needle before and after use .
2. Prepare the smear
a. If you have a solid culture (agar colony), place a small drop of water on a clean slide.
Drag the sterile inoculating needle tip through the edge of colony.
b. Gently spread the mixture into a circle.
A loop of liquid culture can be placed directly on the slide and spread out.
3. Let the smear air dry completely.
4. Heat-Fix the smear.
Smears are heat-fixed by quickly passing the slide through a flame two or three times.
This causes the microbes to stick to the slide and not get washed off during the staining process.
5. Stain the smear.
Place the slide on a rack over the sink. Flood the smear with stain and let it for 60-90 seconds. Rinse gently and blot dry.
6. Observe the slide under low and high-dry lenses to locate, center, and focus the image.
Then, place a drop of oil directly on the stained smear .Turn the oil lens into position and fine focus to observe the cells.
Coccus (cocci pl.)
Bacillus (Bacilli pl.)
Spirillum (Spirilli pl.)
Name the bacterial morphologies (shapes and arrangements) seen
here.
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4
5
6Answers:
1 .Spirillum2 .Coccus3 .Bacillus4 .Diplobacillus5 .Streptobacillus6 .Diplococcus