Exercise 21: Antiseptics and Disinfectants


There are a wide variety of chemical agents available that are supposed to control microbial growth. Two examples of antimicrobial agents are disinfectants and antiseptics. In this exercise, you will test the effectiveness of a variety of antiseptics and disinfectants on a Gram-positive bacterium and a Gram-negative bacterium.



Pseudomonas aeruginosa

Staphylococcus aureus


1 TSA plate


Sterile swabs

Sterile paper disks (1/4 inch)

Pasteur pipettes

Miscellaneous antiseptics and disinfectants


Day 1 (inoculation)

1. Dip a sterile swab into the culture of Pseudomonas aeruginosa

2. Swab a TSA plate over the entire surface by going in one direction; then turn the plate and swab the entire plate going in the other direction.

3. Repeat swabbing the entire plate, swabbing in three directions (by turning the plate).

4. Choose two agents form the basket of miscellaneous antiseptics and disinfectants, or your own from home.

5. Using flamed forceps, remove a sterile 1/4-inch disk from the vial and place it on the inside of the cover of the TSA plate.

6. Use a Pasteur pipette to add a drop of a liquid agent to the disk or squeeze a sample out of the container onto the disk.

7. Use the flamed forceps to transfer the saturated disk onto one-half of the TSA plate. Gently tap the disk so that it adheres to the agar.

8. Repeat the same procedure with another agent, and place the disk on the other half of the TSA plate.

9. Other students will follow the same procedure above with Staphylococcus aureus.

10. Invert all the plates and incubate at 35 degrees Celsius until the next lab period.

Day 2 (Measurement of Disks)

1. Use a millimeter ruler to measure any zone around the disks on each of the plates.

2. Record the results in the Evaluation of Results section.

3. Compare your results with the other students in the class.

My Life as a Machine: Disconnection

Japan feels like home to me. The first time I went to Japan in 2008, I felt like it was a homecoming, like every inch of those islands was celebrating my return to its nature. Coming back to America gave me a heavy weight, and after two years, I returned to Japan alone. The earth felt different but comforting, and I stared at everything, trying to realize what my connection was to the country.

Now, with my acceptance into the JET Program, I comprehended why I yearned Japan so much. It wasn’t just the warm feeling that bubbled up from Japan’s earth into my bones. I knew something people seemed to be oblivious to. Japanese people are rather distant. The superficial politeness was just a by-product of the society–a society so concerned with image, the soul is denied in most cases. Deep down, I want to be disconnected from humanity. I do things that don’t involve me with others.

But I think it’s because I’m scared. And I don’t care. Or maybe I don’t want to peel away the mechanical frame called my skin, because I’ll become as fragile as people.

Life as a Machine: The Pride Gear

Something I thought I could do so easily was throw away my pride. I have so much pride in everything that I do. Whether it’s thinking it or saying it, I have too much pride. Now, like a super hero trying to get stronger, I have to throw it away so I can grow and get better at everything that I do.

Pride is one of those things that can stick to the bottom of your skills and talents until it gums up the elevator lifting to improvement. It’s a gear inside my body that is slowly rusting, and the rusting is becoming contagious. I will lose this gear somehow so I can become a better machine. I may believe that the pride gear is something that can distinguish between people and machine, but in reality, it doesn’t work for anyone. The pride gear will trip anyone until land at the bottom.