Passage IV

Researchers performed the following experiments to evaluate the effectiveness of a disinfectant (chemical) called NoGrow (NG) at stopping bacterial growth.

Experiment 1

Equal amounts of a solution containing the bacterium Escherichia coli (E. coli) were added to 5 test tubes. One sample was not exposed to NG; the remaining 4 samples were exposed to 0.1 mL of NG for different times. The 5 samples were then washed to remove the NG and incubated for 24 hours at 37°C. After the 24-hour period, researchers checked the samples for bacterial growth (see Table 1).

Experiment 2

Experiment 1 was repeated with the bacterium Staphylococcus epidermidis (S. epidermidis). The results appear in Table 2.

Experiment 3

Experiment 1 was repeated with the bacterium Bacillus subtilis (B. subtilis). The results appear in Table 3.

Experiment 4

Four test tubes containing equal amounts of S. epidermidis and 1.0 mL of sterile water were subjected to different temperatures. Samples from each tube were taken periodically. Then the samples were washed, incubated, and checked for bacterial growth as described above. The results appear in Table 4.

Experiment 5

The same procedure described in Experiment 4 was used with 4 tubes containing S. epidermidis and 0.1 mL of NG. The results appear in Table 5.