Bioprospecting

Module 2 - Workspace Skills for Aseptic Technique

This module contains activities that establish a foundation for aseptic techniques and how to perform them in the biology laboratory.

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We suggest setting up stations around the lab space, with a good set of rotations and groups.

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Each activity in this deck contains a separate teacher prep slide for you.

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Teacher Prep

Activity Menu

Activity Goal:

To demonstrate how pervasive contamination transfer is and why aseptic techniques are important to microbiology.

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Station Materials:

Empty Sterile Petri dishes or old unused plates

Inoculating loop or toothpick spreader (any sterile practice tools)

Paper circles or small pieces of paper (to simulate algae)

Optional: Glitter or colored powder (to simulate contamination.

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Steps:

1. Set up a sample station or your classroom desk with items of interest and contaminate and item or a pair of gloves with glitter or fluorescent powder.
2. Have students touch or handle items at the station or on your desk.
3. Use a blacklight or flashlight to reveal the amount of transfer.
1. Turning out the classroom lights helps both blacklight and glitter to shine.
4. Follow up with reflection questions.

Teacher Prep - The Invisible Spread

The Invisible Spread Station

• Come up to the station, and demonstrate how you would use the following equipment.

Aseptic Personal Setup

• How far did the “contamination” spread?
• Did gloves prevent spreading?
• What mistakes contributed to contamination?

In your Group…

…discuss these questions.

• What do we need to do to be ready to minimize contamination risk in our lab?

In your Group…

…get ready to share on this question

The Invisible Spread

• What do we need to do to be ready to minimize contamination risk in our lab?

• Tie back hair as needed
• Secure loose sleeves
• Remove unnecessary items (phones, backpacks, etc.)
• Wash hands thoroughly
• Put on gloves
• Say to yourself “If I touch my pocket, phone, or backpack my gloves are contaminated and must be changed.”

In your Group…

…get ready to share on this question

Activity Goal:

To demonstrate how to handle a petri dish to minimize the risk of contamination.

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Station Materials:

• Empty Sterile Petri dishes or old unused plates
• Inoculating loop or toothpick spreader (any sterile practice tools)
• Paper circles or small pieces of paper (to simulate algae)
• Optional: Glitter or colored powder (to simulate contamination.

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Steps:

• Set up the stations for practice.
• Demonstrate the operation for students.
• Have student’s practice - use the checklist to evaluate each other.

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Teacher Prep - Petri Dish Handling

Petri Dish Handling

Handling Steps

Evaluate your lab partner using these steps and the checklist on the right.

1. Pick up the plate correctly.
2. Open the lid slightly.
3. Insert the “specimen”.
4. Close the lid.
5. Repeat 3 - 4 times smoothly.

Activity Goal:

To practice aseptic transfer techniques to minimize contamination when transferring algae.

Teacher Prep - Aseptic Pipette Transfer Techniques

Practice Round 2: Cross-Contamination Awareness

Students get two different colored water samples.

• Transfer one color to Plate A.
• Use the same pipette for the second color and transfer to Plate B.
• Discuss: What do you observe as far as colors you see? Are they considered clean using aseptic techniques?
• Obtain a clean pipette and transfer one color to Plate A.
• Discard pipette.
• Use a new pipette for the second color and Plate B.
• Discuss: What do you observe as far as colors you see? Are they considered clean using aseptic techniques?

Station Materials:

Transfer pipettes (one per student + extras)

Cups of colored water

Paper towels

Parafilm or wax paper for “mock agar plates” with a designated center circle

Optional: food coloring in two different colors

Practice Round 1: Drop Consistency

Students get one colored water sample

• Aspirate colored water vertically.
• Dispense one drop at the center of their mock plate.
• Repeat 3–4 times using the same consistent pressure.
• Partner observes:
• Are drop sizes similar?
• Is the pipette vertical during aspiration?
• Are they touching the tip?

Aseptic Pipette Transfer Technique

• What makes a good, aseptic transfer using a pipette?

In your Group…

…get ready to share on this question

Part 1: Consistent Volume and Handling

Using one color water, do the following steps:

1. Aspirate colored water vertically.
2. Dispense one drop at the center of your plate.
3. Repeat 3–4 times using the same consistent pressure, placing the drops next to each other.

Part 2: Aseptic Transfer Technique

• Transfer one color to Plate A.
• Use the same pipette for the second color and transfer to Plate B.
• Discuss: What do you observe as far as colors you see? Are they considered clean using aseptic techniques?

• Obtain a clean pipette and transfer one color to Plate A.
• Discard pipette.
• Use a new pipette for the second color and Plate B.
• Discuss: What do you observe as far as colors you see? Are they considered clean using aseptic techniques?

Using two colors of water, perform the following steps:z

Aseptic Pipette Transfer Technique

• So, what are the keys for good pipette work?

• Use a new pipette for each sample.
• Never return unused liquid to the original container.
• Consistent pressure on the pipette bulb
• Don’t touch the container with the pipette.

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In your Group…

…get ready to share on this question

Activity Goal:

To demonstrate how to use the Secchi Stick in the lab to take consistent algae density readings.

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Station Materials:

• Secchi stick (with 90° bend so target is visible from above)
• Clear container (graduated cylinder, tall beaker, or turbidity tube)
• Water with varying turbidity (add small amounts of algae, milk, or diluted clay)
• Stir rod or lid for gentle mixing

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Steps:

• Gently mix the container to ensure homogeneity.
• Open the container carefully.
• Stand directly above the container.
• Hold the Secchi stick vertically.
• Slowly lower the stick into the liquid.
• Stop when the target is no longer visible.
• Hold steady.
• Read depth at the top edge of the liquid (meniscus).
• Record depth in millimeters (mm).
• Remix sample.
• Take two additional readings.
• Calculate an average.

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Teacher Prep - Accurate Secchi Stick Readings

Accurate Secchi Stick Reading

• Gently mix the container to ensure homogeneity.
• Open the container carefully.
• Stand directly above the container.
• Hold the Secchi stick vertically.
• Slowly lower the stick into the liquid.
• Stop when the target is no longer visible - Hold stick steady.
• Read depth at the top edge of the liquid (meniscus).
• Record depth in millimeters (mm).
• Remix sample.
• Take two additional readings.
• Calculate an average.

In your Group, discuss…

…how each of these steps helps you take a better measurement.