Question 1

Why is aseptic technique critical in environmental microbiology research?

Accepted Answer

Aseptic technique prevents bacterial and fungal contamination of reagents, culture media, and environmental samples, while avoiding cross-contamination between samples. Contamination can result in prohibitive costs to replace cultures, especially rare isolates from unique environments that may be irreplaceable. The technique also protects researchers by reducing pathogen transmission during laboratory work.

Question 2

What are the main sources of contamination in a microbiology laboratory?

Accepted Answer

Common contamination sources include airborne microorganisms adhering to dust and lint particles, microbes on laboratory benches and unsterilized equipment, and microbes transferred from the researcher's hair, body, and clothing. Understanding these sources helps guide proper aseptic practices to maintain sterile working environments and protect culture integrity.

Question 3

How does a Bunsen burner create a sterile working environment?

Accepted Answer

A Bunsen burner generates heat that causes air convection, creating an updraft that lifts airborne contaminants away from the flame vicinity. This updraft establishes a sterile field where aseptic experimental work can be conducted safely. The flame also sterilizes tools like inoculation loops and glass rods through direct heat exposure.

Question 4

What is the proper procedure for sterilizing growth media in an autoclave?

Accepted Answer

Dissolve solid medium components in the specified liquid solvent in an autoclavable container with a magnetic stir bar. Loosely cap glass vessels to allow gas expansion during heating. Apply autoclave tape, then sterilize according to manufacturer instructions, typically 20 minutes at 121°C. Verify the tape stripes turned black, indicating proper temperature was reached.

Question 5

How do you aseptically transfer bacteria using an inoculating loop?

Accepted Answer

Sterilize the inoculation loop by passing it through a flame until red hot. For solid agar, gently tap the hot loop on empty agar to cool it, then scrape a single colony. For liquid culture, pass the container mouth through flame 2-3 times, insert the cooled loop, and remove one loopful. Always sterilize the loop after use to prevent contamination.

Question 6

What technique produces isolated bacterial colonies on an agar plate?

Accepted Answer

Streak the inoculation loop back-and-forth across one sector of sterile agar. Sterilize and cool the loop, then make a second streak at an obtuse angle, crossing the first streak on initial strokes only. Repeat sterilization and streaking two more times. Individual colonies appear on the final streak, while a bacterial lawn covers earlier streaks.

Question 7

How are aseptic techniques applied to studying bacteriophages in environmental samples?

Accepted Answer

Researchers grow bacterial cultures under aseptic conditions, then mix soil-derived phage solutions with the bacterial culture and plate onto agar. A bacterial lawn forms on the plate, but plaques—clearings where viruses killed bacteria—appear at infection sites. Phage can then be purified from these plaques for further study using detection of bacteriophages in environmental samples methods.

Technique aseptique en sciences de l'environnement - Quiz d'évaluation