You prepare serial dilutions by adding 10 grams of meat to the first water blank containing 90ml of sterile water. The sample is shaken to mix the contents and 1ml is then taken and added to the second test tube containing 99ml of sterile water. This process is repeated until you have four samples in total. Samples are then taken as per the diagram and added to TSA plates.

The following colony counts are observed:

Pour Plate No. Inoculation Volume (ml) No. of Colonies B1 1 Too many to count B2 0.1 500 C1 1 450 C2 0.1 125 D1 1 <10

 

Question 1 options:

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What is the dilution of Plate B2?

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How is the count of D1 expressed?

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What is the dilution of Plate C1?

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What is the bacteria count of the Sample of meat (cfu/g)?

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What is the dilution of Blank A?

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Which is the countable plate?

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What is the dilution of the countable plate?

50 Iatrens Proble ms 18 1, soil (11.2.g·t 28: noisture) was.added toa90-미 dilution olank for the·ond vhich 10 ml vere removed and added to a 3rd 90-m deteraination of fungi. Ten ml of this initial dilution vas added to a s 90-al blank and shaken, froa blank and shaken. One ml vas extracted from the 3rd blank and plated onto ag ar plates. An average of 57 colonies grew 2. A quantity of soil equaling 9.8 g at i6% noisture was added to a 90-al water blank. The blank was shaken and a 1- volume remov ed and added to a 99-m1 dilution blank twice. One al of the final solution vas plated onto an agar for the detenaination of actinanycetes and bacteria; an average of 105 colonies grew. 3. wet soil totaling 14.3 g at 37% moisture vas added to a 90-ml dilution blank and shaken. Ten al of the initial dilution was added to a 2ad 90-m1 blank and shaken, fol loved by 10 ml of the resulting dilution being added to a 3rd 90-m1 blank. Froa there a 1-al quantity was added to a 99-ml blank and shaken. One- tenth of a ml average of 22.5 colonies grew. of this solution vas added to a plate of Martin's med ium and an 4. A quantity of soil weighing 107 g at 12.5% moisture was added to a bottle containing 900 nl and shaken. A 100-al aliquot of this dilution was added toa bottle containing 900 l. One al of the resulting solution vas added to a bottle containing 999 ml and shaken. Fron this bottle 10 ml of solution vas withdrawn and added to 30-cm petri dishs containing egg albumin agar. An average of 98 colonies grew X A quantity of soil weighing 50.3 g at 25.7% moisture was added to a 250-pl shaken.-Ten al of the initial dilution was added to dilution blank and a 40-1 dilution blank and shaken. This as repeated 3 times. From the last dilution blank ml of solution vas extracted and added to a plate containing Martin's med iun, from which 34 colonies grev. 6. soil (0.92 g at 19% moisture) was added to a test tube containing 9 ml· This vas shaken and 1 ml extracted and added to a 2nd 9-ml blank. Fron the dilution, 0.1 ml was added to 9.9-a1 blanks three times. From the last dilution, a 0.1-al aliquot was added to egg albumin rew. ag ar plates and 34 colonies

Practice SERIAL DILUTION - Equipment and Materials Needed test tube rack 6 test tubes, 12 X 75 mm pipets: 1- 2 ml 2-1 ml solution of food coloring in distilled water (1 distilled water Method 1. Label tubes 1 through 6 and place in rack. 2. Pipet 1.0 ml of distilled water (diluent) in tubes 2-6. ←3. Pipet 1.8 ml of distilled water into test tube #1 .い Pipet 0.2 ml of the peacoormosouton/into tube #1. Tube number 1 now contains twice the volume of any other tube. 4. Mix the contents of tube #1 and transfer 1.0 ml of it into tube #2. Mix contents of #2 and transfer 1 .0 ml of it into tube #3. Continue in this manner until tube #6. 6, 7. Mix the contents of tube 5 transfer 1.0 ml to tube 6. Mix the contents of tube 6 and discard 1.0 ml. 8. Measure the absorbance of each tube using the spectrophotometer at Note: The volume of each tube should be the same. Draw the serial dilution on the back. 490nm (follow the instructions)