6 Environmental Microbiology II Relationship to Class Instruction: Chapters 3, 4, and 10
Answer worksheet Turn in the copies of your observations and sketches at the end of class.
Worksheet due on ________
Purpose of Laboratory
Observation of plates from session I and l record in lab notebook.
Procedure Observation of Plates Special Safety Precautions Discard all biohazard material appropriately. Do not open plates that show a fuzzy growth (molds).
Environmental Samples 1. Collect your plates for observation.
4. What happened to swabs of different environment? Compare and record number and morphology of colonies.
2. Examine the various colony morphologies present on your plate. * DO NOT ever open any plate that has a white fuzzy growth on it. Call the instructor if anything looks fuzzy.*
5. Refer to the table for examples of typical terms used to describe colonial morphology. Practice using these terms to describe colonies to your lab partner.
3. What happened to the plates as they were
6. Draw a few typical colonies (4-5) as
opened for longer times to the air? Record numbers of colonies for the whole class in the table provided. Record the numbers in your lab notebook as well.
examples in your lab notebook. Include the origin of the specimen in the caption, for example: instructor’s computer mouse, button on ATM vending machine.)
Nose and Throat Samples alpha hemolysis. The normal flora of mouth and throat streptococci usually produces alpha hemolysis.
1. Examine your throat culture. Be sure to look at the plate against the light. Can you see a change in the Blood Agar medium itself? Note any changes in the medium itself.
4. Some organisms cause no hemolysis. This is referred to as gamma-hemolysis.
2. Some organisms will cause a total clearing
5. Note and draw the different types of
of the red blood cells; this is referred to as beta hemolysis.
colonies. Include origin of colony (finger, floor, throat, etc.), medium (TSA or Blood Agar) and incubation temperature.
3. Some organisms will cause an incomplete change or greening; this is referred to as
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Growth of microorganisms from air exposure 1.
Enter number of colonies versus time in the table. Use results obtained by the whole class.
Time of Exposure to Air (min)
Number of Colonies
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Average Number of Colonies
Common Descriptions for Colony Morphology Size of colonies correlates to some species Punctiform
Very small dots
.:.:
Small
Colonies with a diameter of 1-2 mm would be considered small
Large colonies
Colonies over 8 mm are considered large
Circular
Round colonies with even borders
Filamentous
Fibrous looking, with stringy extensions
Irregular
Extending unevenly from the center with asymmetrical borders
Loboid
Border of colony appears to extend out in lobes
Rhizoid
The border of the colony appears to extend out like tree roots - see picture and description above
Spindle
The colony is shaped long and thin like a spindle
Spreading or swarming
Edges of the colony appear wavy
Flat
Colony seems even with the surface of the agar
Raised
Colony appears as a mound on the agar
Umbonate
Slightly raised in the center
Pitted
Depressed into the agar
Shiny or Wet
Colony appears shiny and moist
Mucoid
Colony appears covered with mucous
Dry
Colony appears dry and sometimes folded
Colony Size
Shape and Margins
Elevation
Texture
Opaque
Color
Colony is solid, an object behind the colony cannot be seen
Translucent
A colony that appears to allow you to see through it
Colored Colonies
Most colonies have some color - many are just shades of white or grey, but the color is an important characteristic and tool in identification
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