Lab Exercise 3 (Culture Media)

Question 1

What is culture media?

Answer 1

mixture of materials to grow microbes

Question 2

What are the five main ingredients of culture media

Answer 2

Carbon, Nitrogen, Minerals, Buffer, Water

Question 3

Broth vs. solid – what’s the difference?

Answer 3

All culture media can be made in one of two forms: 1) liquid or broth media 2) solid media
BROTH Media- numerous recipes Growth may appear a) Turbidity- cloudy liquid b) Pellicle formation- thin cells flaoting on top of broth c) Sediment- deposit cells of cells at the bottom that will swirl upward if the tube is tapped gently

Question 4

What advantage does solid media have over broth media?

Answer 4

Broth media will maintain their characteristic shape and arrangement better than on solid media
With solid media medium it will remain solid despite metabolic activity b/c most microorganisms do not use agar as a nutrient source Advantage: Solid @ high temp & microbes don’t eat

Question 5

What are some types of solid media? What is the purpose of each type?

Answer 5

Agar tubes (deeps)-used to test the ability of bacteria to catabolize nutrients under anaerobic conditions since air is not readily able to penetrate the media

Agar Slants- used to maintain stock cultures b/c they provide a broad surface for growth and observations, but do not dry out as fast as agar plates

Agar Plates- surface with provide ways to observe and manipulate microbial cultures not available with liquid media, agar tubes or slants. Colonies of individual types can be easily separated from one another for isolation and identification

Question 6

What is agar? Where does it come from? Why do we use it to solidify media?

Answer 6

Agar is a complex polysaccharide produced by marine algae and is ideal for laboratory use. High melting point (97-100) and solidifies @ (42) which is solid @ RT

Question 7

Complex vs. defined – What’s the difference?

Answer 7

Complex (crude ingredients): exact amount of each particular element NOT known EX: natural agar (N.A has beef extract)
Commonly contain extracts of yeasts, meats, or vegetable materials such as soybeans and/or digests of proteins from such sources.

Defines media: chemically defined media all ingredients have chemical formula & amount of each element is known