Aseptic technique
Fri, Oct 2, 2026 · Week 6 · Genetics of Disease (Medical Interventions)
Today's goal: Practice aseptic technique so you can grow a pure culture without contaminating it or yourself.
This is a model of the work you should turn in today. Use it to check your own: match the structure and the level of detail, do not copy it. Your data and wording should be your own.
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. Disinfect the bench and wash your hands, then put on gloves. No food or drink, and long hair tied back.
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 rules for cultures and waste: Treat every culture as if it could be harmful. Tape the lid shut before incubating; an incubated plate stays taped and is read through the lid. Never open an incubated plate. Flood used plates with 10% bleach for at least 20 minutes (or autoclave), then put them in the marked biohazard container, never the regular trash. Disinfect the bench again when you finish.
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: Submit your pre-lab as one PDF to Wk6 Pre-lab: Aseptic technique in Schoology by the end of class today, then bring it to the culturing lab on Monday, October 5.
Turn 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.
Go to Schoology to turn this in.
Submit one PDF. Schoology attaches your name to your upload; on the page itself, write your period and code. Name the file: FirstName LastName - Assignment Title - YYYY-MM-DD.pdf.
Open Schoology PDF upload helpIf you cannot get in, see Mr. Mendoza. Do not skip the work.
Claim ceiling: Today's evidence supports a classroom claim about aseptic technique. It cannot prove causation, diagnose a real patient, or justify action outside this room.
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.
It builds this reusable test skill: Applying aseptic technique to prevent culture contamination.
- Name the concept or data pattern being tested.
- Cross out choices that violate that rule or the evidence.
- Justify the best remaining choice before checking the answer.