Lab Exercise 2
Culture Media
General Purpose Media:
Nutrient Broth and Nutrient Agar
Enriched Media
Selective Media:
Mycological agar
Differential Media
Glucose Fermentation
a. Neutral pH uninoculated tube of glucose
broth with phenol red pH indicator.
b. Fermentation of glucose and acid
production (color change from red to
yellow) (acidic pH)
c. Organism growth, but negative for acid
production (alkaline pH)
a
b
c
Differential Media:
MacConkey Agar
left: no lactose fermentation
right: lactose fermentation
Gel media (in-between liquid broth and
solid agar) is used to test for motility
Spreading out
indicates motility
Sterilization by autoclaving:
15-20 psi at 121°C for15-20 minutes
Bunsen burner flame
Aseptically pouring
agar plates
Agar plates are stored upside down to
prevent condensation.
All labeling is done on the bottom of the agar plate
1. Initials
2. Date (mm/dd/yy)
3. Code # or letter
Environmental sampling
Typical environmental sampling results
Microbes in the Environment. This plate was inoculated with
500 L of indoor air. Approximately how many colonies are on
the plate? How many different bacterial species are here?
2
1
3
4
6
5
7
8
Microbes in the Environment. This plate was inoculated with
a cotton swab that was wiped over a shower drain.
Fungi usually produce large, "fuzzy" colonies (marked F).
Approximately how many colonies are on the plate? How many
are bacterial colonies? How many different bacterial species
are here?
F