Passage II

Samples of Species C bacteria must often be transported from the areas in which they are collected. During transport, the samples are typically packed in ice to keep them alive. However, ice is not always available where the samples are collected.

Scientists studied how lyophilization (a freeze-drying process that doesn't require ice) followed by incubation affects the survival of 2 strains (Strain E and Strain V2) of species C bacteria.

Experiment 1

The scientists placed a 100 uL (1 μL=10^-3 mL) sample of a nutrient medium containing 4 × 10⁶ Strain E elementary bodies into each of 8 sterile test tubes. An elementary body is the infective form of Species C. The sample in each of the tubes was then lyophilized, and each tube was sealed. Two of the tubes were incubated at 4°C, 2 were incubated at 20°C, 2 were incubated. at 30°C, and 2 were incubated at 37°C.

One week after the start of incubation, the percent survival (the percent of the elementary bodies that survived) was determined for the sample in 1 of the 2 tubes at each temperature. Then, 1 month after the start of incubation, the percent survival was determined for the sample in the remaining tube at each temperature. The results are shown in Table 1.

Experiment 2

The scientists repeated Experiment 1, except with Strain V2 instead of Strain E. The results are shown in Table 2.