Thinking Like a Biotechnician
1. After making several batches of sterile LB broth, you see pieces of dust in the broth. Is the
broth suitable to use? How could the dust have entered the bottles?
2. Why is it not advisable to heat or sterilize media longer than necessary?
3. Additional compounds can be added to agar before sterilization (or sometimes after). An
example of this is “milk agar,” in which 2% nonfat powdered milk is added to the agar base.
Lactose-digesting bacteria like to grow on milk agar. How many grams of nonfat powdered
milk should be added to the 125 mL of LB agar to end up with 2% milk LB agar? Show your
calculations.
4. Growing mammalian, fungal, and bacterial cells in or on sterile, prepared media is critical for
their study. Each type has specific requirements for growth. Access the following Web site to
find information that allows you to compare and contrast the ingredients required by E. coli
bacteria cells versus human cells in culture: biotech.emcp.net/BiologyPages.
Record your analysis in your notebook. How many more ingredients are necessary for human
cell culture? Explain why mammalian cells, such as human cells, have so many more required
ingredients in their growth media.
DNA Isolation and Analysis
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