2.9: Results

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1. Draw and describe the growth seen in each of the four broth cultures.

Bacillus subtilis

Growth =

Escherichia coli

Growth =

Micrococcus luteus

Growth =

Mycobacterium phlei

Growth =

2. Observe the growth in the slant cultures and stab cultures for pigmentation and purity.

Agar Slant Cultures of Bacteria (Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0)

3. Using the terms in the Appendix A, compare a single colony of B. subtilis with a single colony of M. luteus. Use a hand lens or a dissecting microscope to magnify the colony.

Single Colonies of Bacillus subtilis	Isolated Colonies of Escherichia coli	Single Colonies of Micrococcus luteus	Single Colonies of Mycobacterium phlei

Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0	Image: Escherichia coli on Luria agar. © Kevin Hedetniemi and Min-Ken Liao, authors. Licensed for use, ASM MicrobeLibrary.	Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0	Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0

characteristics	B. subtilis	M. luteus
Form of colony
Elevation
Margin (edge)
Surface
Optical characteristics: Opaque, transluscent, dull, mucoid, dry, etc.
Pigmentation Pigments can be divided into two basic types: water insoluble and water soluble. If the pigment is water insoluble, as in the case of most chromogenic bacteria, it does not diffuse out of the organism. As a result, the colonies are pigmented but the agar remains the normal color. If the pigment is water soluble (as in the case of Pseudomonas aeruginosa) it will diffuse out of the organism into the surrounding medium. Both the colonies and the agar will appear pigmented. State the color of the pigment (red, orange, green, etc.) and its solubility (water soluble or water insoluble).

4. Observe the results of the three "contamination" plates and note the differences in colony appearances.

5. Observe the demonstration plates of chromogenic bacteria and state the color and water-solubility of each pigment.

organism	Color	Solubility
Micrococcus luteus Note yellow, water insoluble pigment.
Micrococcus roseus Note pink rose, water insoluble pigment.
Mycobacterium phlei Note orange, water insoluble pigment.
Serratia marcescens Note red, water insoluble pigment.
Staphylococcus aureus Note gold, water insoluble pigment.
Pseudomonas aeruginosa Note green, water soluble pigment. Pseudomonas aeruginosa Note light green, water soluble pigment.

Contributors and Attributions

Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS)