02.Growth Curve

# Then plot straight down onto the horizontal

• Notes
• 22

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Then plot straight down onto the Horizontal Arithmetic Time Scale and read off the Time this took. And that’s all there is to it! And finally, a Word about Logarithms: Today’s Exercise was made possible by the generous Contributions of Logarithms, which were developed in the Late 16th Century by the Scotsman John Napier, who realized that any Number -- regardless of Size -- can be expressed by the Power to which a “Base” Number must be raised. So the Number 100 can be expressed as 10 2 . You can multiply any two Numbers by adding their Logs and you can divide any Number by another Number by subtracting the Log of one from the other. That how we did it BC (before Calculators). Logarithms provided the Means for all the Calculations required to design The Golden Gate Bridge, The Bay Bridge, The Empire State Building, the DC-3, Chuck Yeager’s “Glamorous Glynnis”, the Boeing 707, and that Energizer Bunny of the Air, the B-52. The Apollo Missions to the Moon were the first Human Endeavor that could not have been accomplished without the Use of a Computer. _______________________________ “No. Try not. Do... or do not. There is no try.” © 1980 LucasFilm Ltd.

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Lab 2 Page 21 Isolations Pseudomonas The Isolation of Pseudomonas relies on Enrichment to allow that Bacterium to come to dominate the Sodium Benzoate Medium. Pseudomonas is motile so the Benzoate Broth in your Test Tube should appear Turbid (L= crowded) or Cloudy, even though it hasn’t been agitated for 48 Hours. If your Broth is Turbid, use your Sterile Inoculating Loop to aseptically transfer a Loopful of Benzoate Broth to a Benzoate Plate. Use this Loopful of Broth as your Primary Streak, then sterilize your Loop and continue with the Secondary and Tertiary Streaks as usual. (The Plates are made with the same Sodium Benzoate Medium but with 1.5% Agar added to provide a Solid Matrix.) The Benzoate Medium will not allow the Growth of many Bacteria except Pseudomonas , so we expect the Colonies that will appear on this Plate after incubation at 30°C for at least 48 Hours should all be Pseudomonas . However, be forewarned that you can sometimes isolate other Soil Bacteria that can metabolize Benzoate. If your Broth is not Turbid, either proceed as described above on the Assumption that the Density of Pseudomonas is too Low to appear Turbid, or swipe a Loopful from someone else’s Test Tube when they’re not looking. Bacillus The Direct Isolation of Bacillus relies on the Ability of Bacillus Spores to resist Heat. The Pasteurized Soil Suspension was plated on Nutrient Agar and the Spores were allowed to germinate and grow. Since we incubated the Plates under Aerobic Conditions, Clostridium Spores which germinated could not grow. Your Plate will almost certainly contain many Colonies with many different Colony Morphologies. But generally, Bacillus Colonies should have a characteristic Frosted Glass or Matte Construction Paper Appearance. After confirming Colony Morphology, use your Inoculating Loop to gather Bacteria from the Edge of an isolated Colony and streak this onto a fresh Nutrient Agar Plate. If you see other Colonies that seem to be a Bacillus but display different Colony Morphologies, we encourage you to work up Plates of each of these Colonies for subsequent Analysis.
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• Winter '09
• MANN
• Bacteria, Agar plate, Bacterial growth, semi-log graph paper, Microtiter Pipettes

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