Pre-Laboratory Questions
1. Why do bacterial cultures need to be incubated, usually for at least 24 hours, before we can see evidence of bacterial growth that can be observed with the unaided eye?
2. In what ways are the media used in this investigation selective?
3. In what ways are the media used in this investigation differential?
4. Consider a mixture of bacterial species from the same genus, such as Staphylococcus. Some members of this genus are harmful pathogens, while others are not. Would a selective medium alone be a good tool to separate the harmful species from the non-harmful species? Explain your answer.
Post-Lab Questions
1. Would simply adding a pH indicator like phenol red to a general-purpose medium, such as nutrient agar, result in a medium that is selective, differential, both, or neither? Why or why not?
2. Why were you instructed to inoculate each plate with three separate streaks, one of each bacterial species, instead of combining all three species and streaking them all onto the plate together?
3. Blood agar and chocolate agar are commonly-used media in many clinical and research laboratories. Why do you think they were not included in your kit?
4. Were there any discrepancies between what you saw in your experiment and what you expected to see based on the lab manual and your readings in this section?
Pre-Laboratory Questions
1. Why do bacterial cultures need to be incubated, usually for at least 24 hours, before we can see evidence of bacterial growth that can be observed with the unaided eye?
2. In what ways are the media used in this investigation selective?
3. In what ways are the media used in this investigation differential?
4. Consider a mixture of bacterial species from the same genus, such as Staphylococcus. Some members of this genus are harmful pathogens, while others are not. Would a selective medium alone be a good tool to separate the harmful species from the non-harmful species? Explain your answer.
Post-Lab Questions
1. Would simply adding a pH indicator like phenol red to a general-purpose medium, such as nutrient agar, result in a medium that is selective, differential, both, or neither? Why or why not?
2. Why were you instructed to inoculate each plate with three separate streaks, one of each bacterial species, instead of combining all three species and streaking them all onto the plate together?
3. Blood agar and chocolate agar are commonly-used media in many clinical and research laboratories. Why do you think they were not included in your kit?
4. Were there any discrepancies between what you saw in your experiment and what you expected to see based on the lab manual and your readings in this section?
