BIOL306 Exercise 2 - Culturing Bacteria Flashcards

Flashcards cover culture media types, sterilization methods, dilution calculations, and key references from Exercise 2 notes.

What is the purpose of culture medium in microbiology?

To supply nutrients that microbes need to grow.

Name the two physical forms of culture media.

Broth (liquid) and solid media (agar-based).

What is agar and where does it come from?

A solidifying agent derived from seaweed used to solidify culture media.

In agar-based media, at what temperatures do the medium melt and solidify?

Melts at 100°C and solidifies around 42°C.

What are the two main categories of culture media?

Complex media and defined media.

What characterizes complex media?

Contains extracts such as beef heart infusion and yeast extract; the exact chemical composition is not known.

What characterizes defined media?

All chemical components are known and identifiable.

What are beef heart infusion and yeast extract examples of?

Components found in complex media.

Why is the Difco manual important?

It lists many types of media and protocols; serves as a micro media cookbook.

What containers can be used to grow microorganisms?

Tubes, bottles, flasks, and plates.

Why are agar slants used in tubes?

To increase surface area for growth.

What is the purpose of sterilizing media before use?

To kill contaminating bacteria.

Name two sterilization methods.

Autoclave (heat and pressure) and filter sterilization.

When is filter sterilization preferred?

For solutions containing heat-sensitive or labile chemicals.

What does the dilution equation C1 × V1 = C2 × V2 represent?

A formula to calculate how much stock solution to transfer to achieve a desired concentration in a diluent.

Using a 50% stock to make 10 mL of a 5% solution, how much stock is required?

1 mL of the 50% stock mixed with 9 mL diluent.

What does 5% solution correspond to in g per 100 mL?

5 g per 100 mL (0.05 g/mL).

What does 25% solution correspond to in g per 100 mL?

25 g per 100 mL (0.25 g/mL).

What is the Merck Index used for in this context?

To identify chemicals/components specified in defined media.

What is the Difco manual commonly called?

A micro media cookbook with recipes and protocols for many laboratory media.

What is the purpose of observing sterile uninoculated versus inoculated tubes?

To observe differences in growth and contamination, confirming sterilization and inoculation effects.

What plates are observed in Ex 2 besides tubes and plates for bacteria?

A fungal plate and bacterial plates (E. coli and B. megaterium) to compare colony morphology.