The Arizona STEM Acceleration Project
How to make Agar Plates
How to make Agar Plates
A 11th and 12th grade STEM lesson
Miranda Thornton
July 2024
Notes for teachers
List of Materials
Standards
HS.L1U3.23
Obtain, evaluate, and communicate the ethical, social, economic and/or political implications of the detection and treatment of abnormal cell function. ● Diseases, which may be caused by invading microorganisms, environmental conditions or defective cell programming, generally result in disturbed cell function.
● Given a suitable medium, cells from a variety of organisms can be grown in situ, that is, outside the organism. These cell cultures are used by scientists to investigate cell functions and have medical implications such as the production of vaccines, screening of drugs, and in vitro fertilization.
Standards
STEM STandards:
MathQR.SPR.3: Represent numerical summaries and visual displays of real-world data to make informed decisions. Reason, communicate, and describe strengths, limitations, and fallacies of various displays. Encompasses P.S-IC.B.6
Bioscience standards:
7.3 Identify and demonstrate proper use of laboratory balances
1.1 Identify and wear appropriate lab attire and personal protective equipment (e.g., safety glasses or goggles, lab coat, gloves, and closed-toe shoes)
7.10 Identify and demonstrate proper use of hot plate/stirrers
8.1
Demonstrate sterile technique (i.e., maintain lab and equipment hygiene, etc.)
8.2
Identify, prepare, sterilize, dispense, and store culture media
Objective(s):
Today: After this activity students should be able to:
Definitions
Nutrient Agar: The simplest artificial media which are commonly used in the laboratories are Nutrient Broth medium & Nutrient Agar Medium, also known as the Basal Media. These media provide all the basic components that are required by the bacterial cell for the rapid growth in the laboratory.
Seriological pipetting: The ability to measure mililiters of liquid more accurately, liquid chemicals or reagents is a fundamental skill needed in the biotechnology or research lab.
Agenda (lesson time)
Today is making Agar day!
Give students that driving question(what is the proper way to make agar plates?)
How proficient am I with micropipetting and using a digital scale?
Block day is all you need to make agar.(2 hours)
Driving Question
what is the proper way to make agar plates?
How proficient am I with micropipetting and using a digital scale?
How to Make Nutrient Agar (youtube.com)
Hands-on Activity Instructions
Think about the following questions:
1. what is the proper way to make agar plates?
2. How proficient am I with micropipetting and measuring out agar on a digital scale?
Hands-on Activity
Instructions
1. Measure 37g of pre-mixed LB-agar powder per L of molten agar you’d like to make. The� precise mass you measure out will be based on the number of plates you’d like to pour.� For example: If you want to make 8 plates, and you want the volume to be ~30 mL, you will want 240 mL of media total.� Importantly, you will actually make more (~250 mL) in case of a spill or have small errors in measurement. You should also always make a bit more gel-agar mix than you think you’ll need.� For 250 mL of LB-agar, you will need:� (37 g pre-mixed LB-agar powder/L) x (0.250 L) = 9.25 g pre-mixed LB-agar powder.
Hands-on Activity Instructions
2. Transfer the LB-agar powder you’ve measured out into an appropriately sized vessel. (250ml erlenmeyer flask)
3. Transfer the deionized water to the same bottle and swirl to form a medium/agar colloid.
4. Place on the hot plate and put the magnetic stirrer in the flask
5. Watch it untils boils and the mixture is homogeneous.
6. While one team member is watching the agar, another can prepare the plates for pouring.
Hands on activity
Instructions
7. Find an empty section of lab bench
8. Spray down the bench with a 70% ethanol solution and wipe down with a paper
towel.
9. Count out the appropriate number of plates and stack them on your lab
bench.
10. Label the plates’ base with the date, Initials and the medium they will contain
11. Open one plate at a time and begin pouring. Measure your desired amount of agar with a pipette for the first plate to get a good idea of what that volume looks like in your particular plate.
Hands on activity
Instructions
12.For the remainder of the plates, it is appropriate to pour directly from the bottle. Make sure
to swirl your plates after pouring to remove bubbles and ensure an even distribution of agar
over the bottom of the plate. Cap each plate after pouring and stack as you pour.
Note: If your agar partially solidifies in the bottle while you’re pouring, you can re-liquefy
the agar by running it through the autoclave again or by microwaving (if you microwave,
beware of over-boiling!).
13. Leave your plates out on the bench to solidify. It takes roughly 30 min for our plates to
solidify at room temperature, however leave them out at room temperature overnight to
allow them to dry. After overnight drying, place the plates in a plastic bag with an absorbent
material to reduce condensation. The plates are then stored at 4 °C until use.
Assessment
Throughout the activity I walk around and ask those open ended questions.
The students are also graded by a rubric on their performance of pouring the plates. (provided here)
Making Agar plates rubric possible points actual points
Calculations for agar and water(show your work) | 10 no work 20 with work | |
Placed magnetic stir bar in flask | 5 | |
Mixture is Homogenized | 5 | |
Use of serological pipette (20ml) | 15 | |
Properly labeled petri dishes | 10 | |
Lid placed on after agar placed in the plate | 5 | |
Plates stacked, ready for solidification | 5 | |
| | |
Total points | 65 points | |
Differentiation
One way to differentiate in this lesson is to provide some groups with the agar already mixed and then they just need to heat it up and the pour it into the plates.
You can also have examples and parts of the lab done to help out.
You can also put them with students that know what to do and can help them along.
Remediation
Extension/Enrichment
Students who are successful right away can create more plates.
The students can also teach other groups and help them with their plates.