17.7.1: Procedure for Osmotic Pressure

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MEDIA

2 plates of Trypticase Soy agar,
2 plates of 5% glucose agar,
2 plates of 10% glucose agar,
2 plates of 25% glucose agar,
2 plates of 5% NaCl agar,
2 plates of 10% NaCl agar, and
2 plates of 15% NaCl agar.

ORGANISMS

Trypticase Soy broth cultures of Escherichia coli and Staphylococcus aureus;
a spore suspension of the mold Aspergillus niger.

A. OSMOTIC PRESSURE PROCEDURE (to be done by tables)

1. Divide one plate of each of the following media in half. Using your inoculating loop, streak one half of each plate with E. coli and the other half with S. aureus (see Fig. 6). Incubate upside down and stacked in the petri plate holder on the shelf of the 37°C incubator corresponding to your lab section until the next lab period.

a. Trypticase Soy agar (control)
b. Trypticase Soy agar with 5% glucose
c. Trypticase Soy agar with 10% glucose
d. Trypticase Soy agar with 25% glucose
e. Trypticase Soy agar with 5% NaCl
f. Trypticase Soy agar with 10% NaCl
g. Trypticase Soy agar with 15% NaCl

Figure \(\PageIndex{1}\): Inoculation of Salt and Sugar Plates with *Escherichia coli* and *Staphylococcus aureus*. (Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0)

2. Using a sterile swab, streak one plate of each of the following media with a spore suspension of the mold A. niger (see Fig. 7). Incubate the plates upside down at room temperature for 1 week.

Figure \(\PageIndex{2}\): **Inoculation of Salt and Sugar Plates with** **Aspergillus niger.** (Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0)

Contributors and Attributions

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