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Ribit Summer 2011. Microbial Ecology – From Isolation to Identification Dr. Melanie Griffin. Growth media. Sterile source of nutrients and water for bacteria to grow Semisolid media contain dissolved agar which will provide a solid surface for the organisms to grow
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Ribit Summer 2011 Microbial Ecology – From Isolation to Identification Dr. Melanie Griffin
Growth media • Sterile source of nutrients and water for bacteria to grow • Semisolid media contain dissolved agar which will provide a solid surface for the organisms to grow • Broth media contains no agar • Both types of media are incubated for 24-48 hours at 25-45˚C.
Distinguishing by Colony Morphologies What to do: Examine the stock culture plates Record appropriate descriptive terms for the colony morphology
Streak Plate Method 2261-01 Initials; Grp#, date, title Always label the bottom of the plate What to do: • Sterilize a loop and capture a loopful of broth • Streak the plate in 3 or 4 sections, taking care to sterilize the loop between and after each streak
Distinguishing Cellular Morphology Observed with 100X obj
Prepare the bacteria • Prepare a bacterial smear • Suspend one colony in one drop of water on a clean microscope slide • Spread the suspension very thin • Allow the smear to air-dry • Do NOT try to rush this step! • Fix the bacteria to the slide by passing through a flame 2 or 3 times
Gram Staining • Primary stain – flood smear with crystal violet • Rinse with water • Cover smear with iodine - Mordant • Rinse with water • Decolorize – gently rinse slide with acetone-alcohol, 3X • Rinse with water • Counterstain with safranin • Rinse with water • Dry slide with blotting paper
Spore Stain • Trim a piece of blotting paper to the size of the smear • Flood with malachite green dye • Steam over open flame for 5 min • Keep paper wet with malachite dye • Rinse slide with a stream of water • Counterstain with safranin • Blot-dry
Microscope Objectives Start with low power (4X) and work your way up to oil immersion (100X) 4X 10X 100X
The 100X oil immersion lens Add ONE drop of oil to the slide Click 100X objective into place Use course focus (turn very slowly) then fine focus – scan field slowly Image sharpest in the center
Visualize your smears Start with low power and work your way up to oil immersion Observe shape, arrangements, Gram reaction
Rapid Biochemical ID Inoculate test system and incubate overnight Read results using a light background and a UV lamp Get your 10-digit code and email/call/text me for the ID mgriff40@kennesaw.edu