Materials per student patient skin swab and patient

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the other should use your Patient Rectal Swab Bacterium. Materials (per Student): • Patient Skin Swab and Patient Rectal Swab Plates • Inoculating Loop • 3 Glass Slides • DI Water Bottle Procedure: 1. Squirt a Drop of Distilled Water onto your Bench. 2. Pick-up your Loop and sterilize it using your Bunsen Burner. 3. Use your Loop to transfer a Loopful of Water from the Water Drop to the Middle of each of your three (3) Slides. 4. Sterilize your Loop again. 5. Cool your Loop on the Agar and then touch your Loop a bit inside the Edge of an Isolated Colony. Simply touching will scoop up enough Bacteria from that Colony. 6. Transfer these Bacteria to the Drop of Water on your first Slide. Emulsify (L= make milky) these Bacteria in the Drop of Water by using your Loop to smear the Drop of Water out to approximately the Size of a Dime. This is a Smear. Without sterilizing your Loop, proceed to the Drop of Water on your Second Slide. Emulsify the Bacteria as above. And again without sterilizing your Loop, proceed from the Second Slide to the Third Slide. Emulsify. A really good Smear will be just barely visible. If it is creamy or chalky- looking, you scooped-up too much of the Colony. The Bacteria will be so dense that you won ʼ t be able to distinguish Individuals and their Shape. And dense Smears sometimes won ʼ t de-stain (“rinse”) Properly. 7. Sterilize your Loop and return it to its Stand. 8. Allow your Smears to Air Dry. You can blow on your Smear to speed this Process along a bit or you can go into Geisha Mode and use a Folder to fan your Slide. Just be sure that your Smear really is Dry. You want to Heat Fix the Bacteria, not steam Dim Sum.
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Lab 2 Page 16 Background Information for Lab 2 Exercises The Bacterial Growth Curve Bacteria reproduce by Binary Fission. A Bacterium will increase its Biochemical and Structural Components, duplicate its DNA, and then divide into two Bacteria. The Period of Time between each successive Binary Fission is termed the Generation Time (or sometimes the Doubling Time). If we were to give each of you a single Bacterium with a 20 Minute Generation Time (like, E. coli ) immediately after each was produced by Binary Fission at Noon and let you grow it under Conditions in which it was deliriously Happy, in about 20 Minutes you’d have two E. coli . In another 20 Minutes you’d have four E. coli : Time N o . Bacteria Time N o . Bacteria 12:00 1 15:00 512 12:20 2 15:20 1024 12:40 4 15:40 2048 13:00 8 16:00 4096 13:20 16 16:20 8192 13:40 32 16:40 16384 14:00 64 17:00 32768 14:20 130 17:20 65536 14:40 256 17:40 131072 This has some Simple but Profound Implications. Since every Generation results in a Doubling of Cell Numbers, the Number of E. coli in your Culture by 15:00 can be expressed by the Number “2” (since it’s Binary Fission) with the Number “9” (the Number of Generations) as the Exponent. So by 15:00 you’ll have 2 9 or 512 E. coli . And this is why we refer to this as Exponential Growth. Exponential Growth is sneaky. Notice how between 12:40 and 13:00 (20 Minutes) the Culture increases by 4 Bacteria, whereas between 17:40 and 18:00 (again, 20 Minutes) it will increase by 131,072 Bacteria. The Growth starts out fairly slow but very rapidly becomes Explosive. This explains why your Milk will be
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