Its likely that all 3 of your red cap tubes are

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(Turbid [“Cloudy”] + Gas). It’s likely that all 3 of your Red Cap Tubes are Positive (so your First Number is a “3”). Example: 1 Positive + 1 Positive + 1 Positive = 3 Positives = 3 2. Next, determine the Number of Positive “M” (“1000”) Blue Cap Tubes. That’ll give you your Second Number. Example: 1 Positive + 1 Positive + 1 Negative = 2 Positives = 2 3. Do the same with your “C” (“100”) Blue Cap Tubes. Example: 1 Positive + 1 Negative + 1 Negative = 1 Positive = 1 4. So you get the Numbers 3-2-1. Read the Results from the MPN Table on the next Page. Example: 3 - 2 - 1 gives an MPN of 150 Remember, that’s 150 Coliform Bacteria per 100 ml . This indicates that there are approximately 150 Coliform Bacteria per 100 ml of your Sample. Since we only used three Tubes for each Sample, the 95% Confidence Limit is as broad as a Politician ʼ s Promise. In the Case of an MPN of 150, the 95% Confidence Limit is from 30 to 440 Coliforms/100 ml. ________________________________________________________ “By the way, sir, I meant to tell you, there are trees in this forest very similar to elm. And the elm piles of London Bridge lasted six hundred years.“ Six hundred years, Reeves?’ Yes, sir.” Six hundred years... That would be quite something.’ © 1957 Horizon Pictures
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Lab 7 Page 9 MPN Table Set-up your 9 Presumptive Test Tubes and read the Number of Positive Tubes (Tubes with Turbidity and Gas) for each Set. Determine the MPN from the Table. N o . Positive Tubes MPN 95% Confidence Limit 10 ml 1.0 ml 0.1 ml Lower Upper 0 0 1 3 < 0.5 9 0 1 0 3 < 0.5 13 1 0 0 4 < 0.5 20 1 0 1 7 1 21 1 1 0 7 1 23 1 1 1 11 3 36 1 2 0 11 3 36 2 0 0 9 1 36 2 0 1 14 3 37 2 1 0 15 3 44 2 1 1 20 7 89 2 2 0 21 4 47 2 2 1 30 10 150 3 0 0 23 4 120 3 0 1 39 7 130 3 0 2 64 15 380 3 1 0 43 7 210 3 1 1 75 14 230 3 1 2 120 30 380 3 2 0 93 15 380 3 2 1 150 30 440 3 2 2 210 35 470 3 3 0 240 36 1300 3 3 1 460 71 2400 3 3 2 1100 150 4800
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Lab 7 Page 10 Isolations Biochemical Tests Gram Positive Biochemical Tests YGC Plates Check your YGC Plates • Yellow Colonies not surrounded by a Zone of Clearing are Micrococcus luteus . • White Colonies surrounded by a Zone of Clearing are Staphylococcus epidermidis . • Itty-Bitty Colonies so small you can barely see them but surrounded by a Zone of Clearing are Streptococcus lactis . If you ʼ re having difficulty seeing the Zones of Clearing, remove the Right Eyepiece from your Microscope and use is as a 10X Magnifier by looking through it “Backwards”. Micrococcus luteus doesn ʼ t seem to have any particularly noteworthy Smell. Staphylococcus epidermidis absolutely reeks, like dirty Gym Clothes left over the Weekend in a Laundry Bag in your Car ʼ s Trunk. Streptococcus lactis has a light and pleasant Dairy Smell similar to Yogurt. ____________________________________________________________ “Now, there's another important decision that can't be postponed. As most of the British soldiers will be working on the bridge, only a small number will be available for railway work. So, I must ask you, Colonel Saito, to lend us some of your own men to reinforce the railway gang, so that the final stretch of track can be completed as quickly as possible. “ I have already given the order.’ We must fix the daily work quota for your men. At first I thought of setting it at a yard
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