Aseptic technique
Open your materials, follow the steps, then turn in your work.
Practice aseptic technique so you can grow a pure culture without contaminating it or yourself.
1. Open your materials
Use the materials named in the first step below. Open lesson resources.
2. Start the work
List the ways a culture could get contaminated, from air to hands to tools.
Show all 6 required steps
- List the ways a culture could get contaminated, from air to hands to tools.
- Watch or read the aseptic-technique steps and write them in order.
- Practice the motions dry: flaming a loop, lifting a lid briefly, working near the flame.
- Explain why you minimize the time a plate is open.
- Note one safety rule for handling cultures and waste.
- Predict what a contaminated plate would look like versus a clean one.
Lost your place? Lost your place? Check which step you are on: if you have not listed contamination routes yet, do that; if your list is done, write the aseptic steps in order, then dry-practice the motions (flame the loop, lift the lid briefly, work near the flame) before writing why you keep the plate open as little as possible.
Check your work before submitting
- You will be able to describe the steps of aseptic technique.
- You will be able to explain how contamination happens and how to prevent it.
- You will be able to handle cultures and waste safely.
Before lab work: read the safety rules
- Wear the required PPE, keep the bench clear, handle equipment only as directed, and know where the eyewash, sink, and spill kit are before you start.
- Human samples and data stay private: label with a code, never a name, and dispose of materials in the correct waste container, then wash your hands.
3. Turn in your work
DueCheck Schoology- Hand in
- Numbered aseptic technique procedure, contamination routes list, explanation of why plates are kept closed, safety rules for cultures and waste, and contamination prediction sketch.
How to submit and name your file
Keep in notebook; bring to Wednesday's culturing lab.
In Schoology, open your course and the assignment for this lesson. Attach your file, select Submit, and check that it appears in the submission.
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How this lesson connects
Keep using what you learned last class: Should we ban antibiotic use in livestock? Today: Skin, breath, air, and unflamed tools all carry stray microbes, so aseptic technique limits their access to the plate in order to keep the culture pure and the results valid.
Optional: listen or watch a unit review▸
Need help? Warm-up, timing, and directions▸
💡 Big idea: Skin, breath, air, and unflamed tools all carry stray microbes, so limits their access to the plate in order to keep the pure and the results valid.
- 0-10 minBrainstorm and list every possible route: air, hands, tools, talking, surfaces
- 10-25 minRead or watch the steps; write them in numbered order in your notebook
- 25-45 minDry practice: simulate a loop (without flame), lifting a lid briefly with wrist only, working near the lab bench edge away from air currents
- 45-58 minExplain in writing why you minimize the time a plate is open; connect to the routes listed earlier
- 58-68 minWrite one rule for handling bacterial cultures and one for disposing of used materials
- 68-80 minDraw and describe what a contaminated plate would look like versus a pure- plate
- • is the single most important skill in microbiology; without it, every experiment is meaningless.
- • Hospitals use to prevent infections during surgery; you will use the same principles Wednesday in this lab.
- • Today you learn and practice the motions before any live cultures are involved.
- • Exit goal: a numbered checklist in your notebook and a dry run of every physical motion you will use tomorrow.
- • is a set of practices designed to prevent of sterile materials and biological cultures.
- • Common routes include: air currents, skin contact, talking or breathing near open plates, and unsterilized tools.
- • Contaminated plates grow mixed colonies that cannot be used to draw conclusions about a single bacterial strain.
PLTW connection and today's work
Open Activity 1.2.3 Attack of the Superbugs in myPLTW and review the culturing protocol before the lab.
Today's stopping point: Monday CER should be posted; pre-lab plan due today.
PLTW activity titles identify the course connection. If your account will not open, use the posted materials for today and tell Mr. Mendoza. Do not mark an online activity complete unless you completed it.
Course connection
- Project 1.2.3 Attack of the Superbugs
Use the turn-in directions at the top of this page. Do not create a second submission unless your teacher asks for one.
Show another explanation or a smaller first step
Need help? Choose a starting point
Finish the assigned lab safely before starting extra practice.
Lesson resources: reading, slides, and vocabulary▸
The deck carries the prior idea forward, lets you inspect an analogy, maps the rule to biology, and ends with the same evidence decision and exit ticket used on this page.
Generated from this lesson's canonical data with a red-team citation check.
Should we ban use in livestock?
Skin, breath, air, and unflamed tools all carry stray microbes, so limits their access to the plate in order to keep the pure and the results valid.
An airport checkpoint uses an ID check, a metal detector, and an X-ray scanner.
- What can the ID check detect?
- What might set off the metal detector by mistake?
- Why do we need the X-ray if we already checked their ID?
A decision is stronger when the test fits the question and its limits are known.
Medical decisions also depend on biology, patient context, ethics, and professional judgment.
- • The ID check maps to confirming patient identity.
- • The metal detector maps to a rapid, non-specific screening test.
- • The X-ray scanner maps to a detailed, specific diagnostic test.
Driving question: You are about to grow one bacterial strain on a plate, but skin, breath, air, and an unflamed loop are all crawling with other microbes. Which specific moves keep those contaminants off your plate?
What you already know: Should we ban use in livestock?
New idea: Skin, breath, air, and unflamed tools all carry stray microbes, so limits their access to the plate in order to keep the pure and the results valid.
Visual or model: F1. F1. A lesson illustration or teaching diagram for Aseptic technique. Use it with E1-E3; it is a model or context image, not experimental or patient data. What to notice: Trace the labeled testing, treatment, or biological process and identify where evidence limits the decision.
- Observe or measure the relevant feature in .
- Organize the observation with a stable evidence ID.
- Apply this rule: A decision is stronger when the test fits the question and its limits are known.
- Choose the option the evidence supports and state the limit of the conclusion.
Real biomedical example: You are about to grow one bacterial strain on a plate, but skin, breath, air, and an unflamed loop are all crawling with other microbes. Which specific moves keep those contaminants off your plate?
What the evidence supports: E1-E3 and F1 support the daily take-home when the response meets the stated success criteria.
What it cannot prove: The package does not support claims beyond this lesson's or any real patient diagnosis.
- • : A set of careful practices used to keep microbes out of a sterile area, protecting samples, cultures, and patients from .
- • : A population of microbes or cells grown on purpose in a nutrient medium so they can be studied, identified, or tested.
- • : A visible cluster of identical microorganisms growing on a plate, all descended from a single original cell.
- • : The slowing or blocking of a process, such as an stopping bacteria from growing or a molecule shutting down an .
- • : A change in the ; some change a enough to cause disease, many do not.
- • : The passing of genes between organisms, often bacteria, without reproduction, a major way resistance spreads.
Use it now: Choose one decision option. Cite E1 and E3, then explain how the rule connects the evidence to your choice.
Go further, optional: The source links below are optional enrichment. Every fact required for today's local evidence decision appears in this lesson package.
Laboratory depends on matching each identified hazard to an appropriate containment practice, protective measure, and stop-work condition before the procedure begins.
Limit: The lesson check does not replace the site-specific SDS, approved procedure, teacher supervision, or emergency plan.
A decision is stronger when the test fits the question and its limits are known.
Limit: Medical decisions also depend on biology, patient context, ethics, and professional judgment.
You can describe the steps of .
Limit: E3 defines the classroom product or success criterion. It is not independent scientific evidence and cannot justify a clinical or causal claim.
PLTW-GEND-2026-10-02 · Simulated classroom evidence scenario
Your role: medical interventions team member
Decision: Your team must decide what the evidence from supports before submitting the pre-lab readiness record named on today's page.
- • Predict what a contaminated plate would look like first, because you cannot yet tell a mixed plate from a pure one.
- • Flame the loop and keep the lid open for the shortest time, because skin, breath, and air carry microbes.
- • Work anywhere the bench and your hands look clean, since comes from obviously dirty things you can see.
Response: State one choice, cite at least two evidence IDs, explain the rule that connects them, and add one limitation. Submit it as the pre-lab readiness record.
Claim ceiling: Today's evidence supports a classroom claim about . It cannot prove causation, diagnose a real patient, or justify action outside this room.
Mean = sum of values / number of values. Median = middle ordered value. Range = maximum - minimum.
For 2, 4, 4, and 10: mean = 20 / 4 = 5, median = 4, and range = 10 - 2 = 8.
Mean, median, and range keep the measurement unit. Order the values before finding the median.
Calculate the requested summary for today's supplied values, then write what it reveals and what it hides.
- • The solution must address the stated need in .
- • The decision must be supported by E1-E3.
- • The final product must make the success criteria visible.
- • Complete the work inside the 80-minute block.
- • Use only supplied or teacher-approved materials and evidence.
- • Do not trade , accessibility, or privacy for speed.
- • and evidence quality: must pass before scoring other criteria.
- • User need and effectiveness: highest scored criterion.
- • Time, cost, and ease of use: compare only after and effectiveness pass.
Test evidence: For each option, record the E1-E3 result that supports or fails each criterion. Do not assign a score without a named observation.
- Version or option tested
- Criterion met or missed
- Evidence ID and result
- Revision made
- Reason for the revision
- Need and user
- Criteria and constraints
- Chosen option and evidence
- Test result
- Revision and reason
Students often think Students often think mainly comes from obviously dirty things, so as long as their hands look clean and the bench looks clean, the plate is fine.. The trap: That is a trap because the biggest routes are invisible: normal skin, ordinary room air currents, and the droplets from talking or breathing near an open plate all carry microbes, which is why you flame the loop, keep the lid open for the shortest possible time, and work near the flame rather than trusting how clean a surface looks.
Contamination routes (how unwanted organisms get in):
- Air currents carrying dust and microbes onto an open plate
- Skin contact from touching the agar or the loop tip
- Talking, coughing, or breathing over an open plate
- Unsterilized tools, like a loop that was not flamed
Aseptic technique, in order:
1. Clean the work surface and wash your hands, then put on gloves.
2. Light the burner and work in the rising warm air near the flame.
3. Flame the inoculating loop until it glows, then let it cool a few seconds.
4. Lift the plate lid only partway and only for as long as you need.
5. Streak the sample, then close the lid right away.
6. Re-flame the loop before setting it down so nothing is carried out.
Why minimize open time: Every second a plate is open, airborne microbes can settle on the agar. Keeping it open as briefly as possible lowers the chance that anything other than my sample starts growing.
Safety rule for cultures and waste: Treat every culture as if it could be harmful. Never open an incubated plate at your seat, and dispose of plates and used tools in the marked biohazard container, never the regular trash.
Prediction: A clean plate will show only one kind of colony along my streak lines. A contaminated plate will show extra colonies of different colors or shapes, often in spots where I did not streak.
This model shows the level of evidence and organization needed to complete: Completes the pre-lab prep for the culturing lab: an ordered aseptic procedure, a contamination-routes list, an explanation of why plates stay closed, safety rules, and a prediction of clean versus contaminated growth.
- Identify the purpose, hazards, and required controls.
- Write the procedure in a usable order.
- Confirm materials, measurements, and waste handling before starting.
Keep the structure. Replace the question, facts, measurements, and evidence. Then recheck units, vocabulary, and whether the conclusion goes beyond the evidence.
Also due today: Keep this pre-lab in your notebook and bring it to the culturing lab.
- CER:
- Claim, Evidence, Reasoning: make a claim, back it with evidence, explain your reasoning.
- SOP:
- Standard Operating Procedure, the exact steps to follow (especially in a lab).
- Tracker:
- Your PLTW progress log where you record completed evidence.
- myPLTW:
- The PLTW course site where you do the online activities. Find it in Clever with your Microsoft sign-in, right next to Schoology.
Tap the speaker to hear a term. Add two of these to your notebook glossary with a definition and an example in your own words.
Pick just 2 or 3 words from today and make them yours: write what each one means in your own words, name the context clue or evidence that helped, then give one example from what you actually did in Aseptic technique. Try your own words first; the glossary is there if you get stuck. This is voluntary and counts as extra credit, so keep it short.
Saved on this device. Show Mr. Mendoza or add these to your notebook glossary to claim the extra credit.
Classroom documents for this lesson are posted in Schoology. Open Clever, then Schoology, and find each one by the name shown on its card.
Use this if you were absent, got stuck, or need another pass before you submit the lesson artifact.
Placement rationale
Matched Culturing, , superbugs by path:Medical-Interventions/Unit-1_How-to-Fight-Infection/00_Unit-Overview. Score 126. Visibility: student-schoology (student-facing resource; link through Schoology rather than local path).
Open this when the class reaches this activity and use it to complete the required lesson artifact.
Placement rationale
Matched Culturing, , superbugs by path:Medical-Interventions/Unit-1_How-to-Fight-Infection/1.2_-Treatment. Score 126. Visibility: student-schoology (student-facing resource; link through Schoology rather than local path).
Sign in to Clever with your district Microsoft account to open Schoology or myPLTW. Follow today's posted steps. If myPLTW will not open, use the posted alternative and tell Mr. Mendoza. Turn in your completed work through the Schoology assignment.
Practice: try a question, then check your answer▸
Claim ceiling for this check: Today's evidence supports a classroom claim about . It cannot prove causation, diagnose a real patient, or justify action outside this room.
Explain why you keep the plate lid open for the shortest time possible during streaking, and name one thing that could contaminate it in that open window.
Write an answer and pick a confidence to unlock the key.
Fast retrieval with instant answers, not the commit-then-reveal check above. Try each from memory first: write what you remember about the earlier units, then check yourself here.
Missed class or ready for more?▸
Run this before you touch the bench. It is built from the real lab procedure, so the decisions you make here are the ones you will make with the equipment in your hands.
Before Wednesday's culturing lab: review your numbered aseptic technique checklist; memorize the motions for lid handling and streaking; confirm you know the location of the bleach solution and biohazard waste bag before touching any culture materials.
Finish the checklist before you handle any material.
- • Wear the required PPE, keep the bench clear, handle equipment only as directed, and know where the eyewash, sink, and spill kit are before you start.
- • Human samples and data stay private: label with a code, never a name, and dispose of materials in the correct waste container, then wash your hands.
- 1Before materials are handled, identify the purpose, variables or comparison, controls, measurement units, and stop-work condition.
- 2List the ways a culture could get contaminated, from air to hands to tools.
- 3Watch or read the aseptic-technique steps and write them in order.
- 4Practice the motions dry: flaming a loop, lifting a lid briefly, working near the flame.
- 5Explain why you minimize the time a plate is open.
- 6Note one safety rule for handling cultures and waste.
- 7Predict what a contaminated plate would look like versus a clean one.
- 8Record each result in the prepared table before interpreting it. Mark missing, repeated, or invalid results truthfully.
- 9Complete the named cleanup and waste route, remove PPE safely, wash hands when required, and confirm the station is ready for the next group.
| Trial or sample ID | Independent condition | Measured result with units | Observation before interpretation | Quality-control note |
|---|---|---|---|---|
Before the procedure, predict the result and cite the rule behind the prediction.
After the procedure, compare the result with the prediction and name one limitation or source of uncertainty.
What today's skills lead to. These are real health-science careers this course builds toward. Tap one to see, on the US Department of Labor's O*NET site, what the job actually involves, what it pays, and how fast it is growing.
The bench work needs equipment you do not have at home. Do the thinking half now: read the procedure, write your prediction, and set up your data table so it is ready.
Back in class. Ask Mr. Mendoza for the class data set, or for a bench slot to run it yourself. Do not submit a Pre-lab with invented numbers.
Class still runs. Complete the online activity above (it's self-guided). Need the concept taught without a teacher? Use this authoritative explainer:
CDC Antibiotic Resistance- CompleteEvery required part of the artifact is present, nothing left blank.
- AccurateThe science and the data are correct and match the evidence.
- Scientific reasoningYou explain your claim with evidence and reasoning (CER), not just an answer.
- Professional communicationClear, organized, labeled, and written the way a clinician or scientist would.
- SubmittedGo to Schoology to turn this in. Submit one PDF. Put your first and last name in the document header. Name the file: FirstName LastName - Assignment Title - YYYY-MM-DD.pdf. If you cannot get in, see Mr. Mendoza. Do not skip the work.
- Error analysis and method · counts doubleName a specific limit of the method and how it moved your result, and compare what you predicted to what happened. "Human error" does not count; say what about the procedure or instrument caused it.
This week
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