A sample of Earth Alive Soil Activator was diluted by transferring 1 gram into a 9 ml dilution blank (tube A) and then serially diluted five (5) more times by transferring 1 ml of a previous dilution into a tube of 9 ml of sterile water. After making these serial dilutions, 2 ml samples were taken from tubes D, E, and F, added into empty petri dishes, and molten PCA was poured into each petri dish. Tubes A, B, and C were heated in a 80˚C water bath for 30 minutes, 2 ml samples of these tubes were added into empty petri dishes, and molten PCA was poured into each petri dish. These plates were allowed to solidify, and they were incubated at 35˚C for 48 hours. After the incubation period, you counted CFUs on all 6 plates. The results of your CFU counts are contained in table 1. Table 1. CFU counts for 3 plates from the heated dilutions (A-C) and the 3 plates from the non-heated dilutions (D-F) # CFUs Not heated Heated A -- 400 B -- 45 C -- 6 D 350 -- E 31 -- F 2 -- Based on the procedure described and your CFU counts, calculate the CFU/g for heterotrophs and endospore-forming bacteria. For your CFU/g answers, copy and paste this format: 1.02x10^exponent (do not add spaces). You do not need to include units in your answers. Total dilution Volume plated (ml) CFU/g Heterotrophs Endospore-formers
A sample of Earth Alive Soil Activator was diluted by transferring 1 gram into a 9 ml dilution blank (tube A) and then serially diluted five (5) more times by transferring 1 ml of a previous dilution into a tube of 9 ml of sterile water. After making these serial dilutions, 2 ml samples were taken from tubes D, E, and F, added into empty petri dishes, and molten PCA was poured into each petri dish. Tubes A, B, and C were heated in a 80˚C water bath for 30 minutes, 2 ml samples of these tubes were added into empty petri dishes, and molten PCA was poured into each petri dish. These plates were allowed to solidify, and they were incubated at 35˚C for 48 hours. After the incubation period, you counted CFUs on all 6 plates. The results of your CFU counts are contained in table 1.
Table 1. CFU counts for 3 plates from the heated dilutions (A-C) and the 3 plates from the non-heated dilutions (D-F)
| # CFUs | ||
| Not heated | Heated | |
| A | -- | 400 |
| B | -- | 45 |
| C | -- | 6 |
| D | 350 | -- |
| E | 31 | -- |
| F | 2 | -- |
Based on the procedure described and your CFU counts, calculate the CFU/g for heterotrophs and endospore-forming bacteria. For your CFU/g answers, copy and paste this format: 1.02x10^exponent (do not add spaces). You do not need to include units in your answers.
| Total dilution | Volume plated (ml) | CFU/g | |
| Heterotrophs | |||
| Endospore-formers |
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