Aseptic Technique

Summary

This instructional video outlines the critical steps for aseptic technique, ensuring bacteria transfer without contamination. Key tools include inoculation loops and needles, and a Bunsen burner for sterilization. The video demonstrates how to transfer bacteria from liquid cultures to petri dishes and other liquids, and from petri plates to stab cultures. It emphasizes the importance of flame sterilization and proper handling to maintain a sterile environment.

Takeaways

• 🔬 Aseptic technique is essential for transferring bacterial monocultures without contamination.
• 🛠️ Common tools used for bacterial transfers include the inoculation loop and inoculation needle.
• 🔥 Proper use of a Bunsen burner is critical, including adjusting the gas and oxygen to control the flame.
• 💡 The hottest part of the Bunsen burner flame is the tip of the blue cone, ideal for sterilizing tools.
• 🧴 Sterilized inoculation tools should never be placed on any surface to prevent contamination.
• 📦 When transferring bacteria from a liquid culture to a petri dish, ensure the lid is held as a shield to prevent airborne contamination.
• 🔄 Spread bacteria evenly on the plate by rotating it a quarter turn between spreads.
• 🔁 When transferring bacteria between liquid cultures, both the culture and media containers should be passed through the flame before and after dipping the inoculation loop.
• 🧫 Transferring bacteria from a petri plate to a stab culture involves making three deep stabs in the nutrient agar after collecting the bacteria.
• ⚗️ Testing for coolness of inoculation tools can be done by lightly tapping them on a clear area of the agar plate before use.

Q & A

What is the purpose of aseptic technique?

Aseptic technique is used to transfer a bacterial monoculture into a fresh medium without introducing any contaminating microorganisms.

What are the two most commonly used tools for transferring bacteria?

The two most commonly used tools for transferring bacteria are the inoculation loop and the inoculation needle.

How do you light a Bunsen burner for aseptic technique?

To light a Bunsen burner, close the valve at the base, cover the vents by rotating the collar, then slowly turn on the gas until the gas ignites the burner. Adjust the height of the flame by controlling the amount of gas.

How can you adjust the temperature of the flame on a Bunsen burner?

The temperature of the flame can be adjusted by rotating the collar to control the flow of oxygen. The coolest flame is yellow and orange, a medium flame is blue, and the hottest flame is a roaring blue flame with a clear blue cone in the middle.

How is an inoculation tool sterilized in aseptic technique?

Inoculation tools are sterilized by passing them through the hottest part of the flame.

Why should sterilized inoculation tools not be set down on any surface?

Once sterilized, inoculation tools should not be set down on any surface to prevent contamination from other surfaces.

How do you transfer bacteria from a liquid culture to a petri dish?

After flaming a loop, remove the lid from the container of liquid culture, pass the mouth through the flame, dip the loop into the liquid culture, flame the mouth again, and then transfer the bacteria to the petri plate by spreading it over the entire surface.

What is the purpose of holding the petri dish lid over the base while transferring bacteria?

Holding the lid over the base acts as a shield to prevent contaminants from falling onto the plate during the transfer of bacteria.

How do you ensure even distribution of bacteria on a petri dish?

To ensure even distribution, spread the bacteria over the entire surface of the plate in all directions, rotating the plate a quarter turn between spreads.

How do you transfer bacteria from a liquid culture to another liquid?

After sterilizing an inoculation loop, remove the lid from the container of liquid culture, pass the mouth through the flame, dip the loop into the liquid culture, flame the mouth again before replacing the lid, then dip the loop with bacteria into the tube of liquid media, flame the mouth of the tube, and replace the lid.

What is the process for transferring bacteria from a petri plate to a stab culture?

Sterilize an inoculation needle by passing it through a flame, allow it to cool, test for coolness by tapping it on the agar plate, then gently rub the needle over a single colony to transfer bacteria to a culture tube filled with nutrient agar.

How do you sterilize an inoculation loop when transferring bacteria from a petri plate to a liquid?

Pass the inoculation loop through the flame to sterilize it, let it cool, test for coolness by tapping it on the agar plate, then dip the loop with bacteria into the tube of liquid media, pass the mouth of the container through the flame, and replace the lid.