Experiment 1- Aseptic Techniques
1. Result of tube transfer
|Time (hour) |Sample |Control |
|1 |Unchanged |Unchanged |
|2 |Unchanged |Unchanged |
|3.25 |Slightly turbid |Unchanged |
Explanation: By comparing sample tube with control tube, the turbidity of control tube was unchanged. It is because the inoculating loop was framed before immersing into broth culture. These microorganisms were killed in high temperature, so that none of them grew in the culture. The control tube kept unchanged. While the sample tube turned slightly turbid after 3 hours. This indicated that microorganisms grew in the culture. But the process was slow and turbidity change was not obvious due to small amount of microorganisms were transferred. Therefore, it had better to immerse into inoculum source twice to obtain more sample.
2. Bacillus subtilis has irregular form, undulate margin with flat elevation. While Staphylococcus epidermidis has circular and punctiform form, convex elevation and entire margin. Pseudomonas aeruginosa has raised elevation, circular form and undulate margin. Saccharomyces cerevisiae has convex elevation, entire margin and punctiform. Escherichia coli are circular form, raised elevation and entire margin. Some of them have erose margins.
3. The correct answer is c. inoculating loop should be flame sterilized before transferring the culture. It is because microorganisms exist in everywhere. The inoculating loop is contaminated by other types of microorganisms easily. If the inoculating loop does not be flame...