How do we prove bacteria are ubiquitous?

4) Why is agar incorporated into the growth medium used?

        Agar is incorporated into the growth medium because it allows microorganisms to grow.

Materials:

• Gloves
• Goggles
• Ring stand
• Wire gauze
• Test tube (agar butt)
• Test tube holder clamp
• Incubator
• Magnifying lens
• Wax pencil
• Lab coat
• Bleach
• Beaker 3/4 full of H2O
• Bunsen burner
• sterile cotton swabs
• Matches
• Sterile Petri dish (4 each group)
• Masking tape
• Worksheet of colony descriptions

Procedure:

• Donne gloves, lab coat, goggles.
• Bleach table top.
• Set up hot water bath (ring stand, wire gauze, beaker 3/4 full of H2O.
• When beaker starts to boil add agar test tube butt (be sure to remove cap first).
• Wait until agar melts (it will become a golden yellow liquid).
• Obtain sterile Petri dish.
• Using a wax pencil, label all four quadrants of Petri dish.
• Using your best sterile technique, pour the agar into the Petri dish, partially replace the cover. Wait until it gels (do not touch inside of the dish cover or bottom).
• After the gel cools/ hardens, obtain a sterile cotton swab
• Each student at the table will inoculate on of the four Petri dishes; swab the bleached table, an electrical outlet, a used but still functional light bulb, and the drain of a sink.
• Inoculate the Petri dish gently as not to tear the agar or scratch it in anyway.
• After inoculation, use masking tape around the diameter of the dish and its invert.
• Inoculate the inverted Petri dish for 48 hours at 34 degrees Celsius.
• Do not open the Petri dish.
• After 48 hours observe Petri dish with magnifying lens.
• Draw observations.

Conclusion:

1) What is a bacterial colony?

        A bacterial colony is when there is a visible growth of microorganisms. Bacterial colonies grow in many forms.

2) Why is the Petri dish inverted in the incubator?

        To prevent condensation from forming, the dishes must be placed inversely in the incubator.

3) List terms and define the term used to describe colonial morphology?

        Colonial morphology refers to the form and structure of organisms. Such terms include the colony’s surface which can be smooth, rough, and wrinkled. Optical characteristics include translucent, dull, glossy, multi-colored, and hazy looking colonies. Most importantly the forms of bacteria, which include, circular, irregular, spindle, filamentous, and rhizoid shapes.