Making a Streak Plate

Summary

This video tutorial teaches the street plate technique for isolating a single bacterial colony. It involves splitting a plate into quadrants and diluting bacteria with a sterilized loop. The process starts with adjusting the Bunsen burner's flame, which is crucial for sterilization. The loop is used to streak bacteria across the plate, with each quadrant receiving a streak and subsequent dilution. After streaking all quadrants, the plate is inverted and incubated at 37°C for 24-48 hours to allow colony growth for examination.

Takeaways

• 🔬 The street plate technique is used for isolating a single colony from a bacterial culture.
• 🔥 A Bunsen burner is used to sterilize the inoculating loop and to control the flame temperature.
• 🌡️ The coolest flame is yellow and orange, while the hottest is a roaring blue flame with a clear blue cone.
• 🔍 The tip of the blue flame cone is the hottest part, ideal for sterilization.
• 🔄 Start by closing the valve at the base and cover the vents before igniting the gas.
• 🔄 Adjust the gas and oxygen flow to control the flame's temperature.
• 🌀 Gently scrape a colony from the plate's surface to collect it on the loop.
• 📍 Transfer the bacteria to an LB agar plate and streak it in quadrants.
• 🔄 After each streak, flame the loop to sterilize it before proceeding to the next quadrant.
• 🔄 Rotate the plate 45° after each streak to ensure even distribution of bacteria.
• 🔄 Repeat the streaking process four times, once in each quadrant.
• 🔄 After completing the streak plating, invert the plate and incubate at 37°C for 24 to 48 hours.

Q & A

What is the street plate technique?

The street plate technique is a method used to isolate a single colony from a bacterial culture by splitting the plate into quadrants and diluting the bacteria repeatedly as the loop is streaked through each quadrant.

How do you start a Bunsen burner for the street plate technique?

To start a Bunsen burner, close the valve at the base, rotate the collar to cover the vents, slowly turn on the gas until you hear it ignite, and then 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.

What is the hottest part of the flame on a Bunsen burner?

The hottest part of the flame is the tip of the blue cone in the roaring blue flame.

How do you sterilize the inoculating loop before using it in the street plate technique?

To sterilize the inoculating loop, pass it through the hottest part of the flame and allow it to cool. You can also lightly touch the loop on an empty spot on the bacterial plate to ensure it is cool.

How do you collect a bacterial colony onto the loop?

Gently scrape a colony from the surface of the plate so that it collects on the loop.

What should you do after transferring the bacteria to the LB agar plate?

After transferring the bacteria, gently rub the loop back and forth across the top left corner of the plate about 10 times to spread the bacteria.

How do you perform the streaking process in the second quadrant of the plate?

Rotate the plate 45°, draw the loop through one end of the first streak, and rub the loop back and forth in the second quadrant about 10 times.

Why is it important to flame the loop after each streaking?

Flaming the loop after each streaking is important to sterilize it and prevent cross-contamination between quadrants.

What should you do after completing the streak plating?

After completing the streak plating, invert the plate and place it in an incubator at 37°C for 24 to 48 hours to allow the colonies to grow.

How long do you need to incubate the plate after performing the street plate technique?

The plate should be incubated at 37°C for 24 to 48 hours to allow the bacterial colonies to grow.