Introduction to Aseptic Techniques

Part of an Access Excellence Lesson (http://www.accessexcellence.org/AE/AEC/AEF/1996/ziegenhirt_microbe.html)

Laura Ziegenhirt

Modified to fit the PULSE curriculum

Time: / 1 class period
Preparation Time: / Time needed to prepare sprays
Materials per team of students / Exercise Two:
Disinfectant in spray bottles (50% Lysol) ,old rags
”bacto-broth” & “bacto-light” (hand held black light)

Abstract

This is part of an arrangement of classic exercises by Laura Ziegenhirt that introduces students to bacteria and aseptic microbiology laboratory techniques. The sequence of lessons and experiments presents a series of important introductory concepts:

Lesson 1-Assesses pre-knowledge of bacteria and aseptic techniques and teaches students how to prepare a work area

Lesson 2 - Students learn how to pour, label, streak, seal and store plates in an incubator

Finally Lesson 3, an addition to Laura Ziegenhirt’s lessons, asks students to articulate what they have learned via an informational laboratory poster.

The content exercises and the lab skill exercises run side by side. The students will determine the conditions necessary for bacterial growth as well as the techniques used to culture and isolate bacteria.

Objectives

Students will be able to:

1.  prepare a work area

National Science Education Standard

Content Standard C– Life Science

Students should develop understanding of the interdependence of organisms

Human beings live within the world’s ecosystems

Teacher Background

Resources

Microbes from http://www.niaid.nih.gov/publications/pdf/microbesbook.pdf - (copyright 2001)

This book goes over the four main types of microbes and their importance in our lives.

Activity

Exercise 1-Assessing Pre-knowledge

Start the class by asking them to respond to the following statement in their journals or notebooks:

In your journals answer the following questions:

What are bacteria? Are they good or bad? What do they look like? Where do you find bacteria? Where do bacteria grow?

After students have had sufficient time to respond to these questions discuss their responses as a class. Students sometimes don’t come up with questions easily, so discussing as a class what they know and what they don’t know gives more foundation for developing questions.

Exercise 2 – Learning to prepare a work area

Preparation: Before class prepare the following:

i.  Spray bottles filled with a solution of 50% Lysol.

ii.  1 small bottle of “bacto-broth” made from fluorescent Elmer’s glue (any color) diluted with water.

iii.  Spread “bacto-broth” on the students’ lap tops and water faucets

During class:

i.  Explain to the class that when they handle bacteria they need to be very careful and treat everything as a pathogen. When they work with bacteria it is very important to disinfect the entire work area before and after the completion of each day’s activity.

ii.  Further explain that “As an exercise to demonstrate the effort required to be thorough in disinfecting their work place, including all nooks and crannies, we have developed a way to visualize bacteria. “Bacto-broth” was spread on the lab area prior to class. Your job is to disinfect your lab station and eliminate all traces of the “bacto-broth.” Our special “Bacto-broth” detector light will be used to inspect your lab area after you have wiped it down. This special bacto illuminator will allow us to see any remaining traces of bacto-broth.

iii.  Students should then use the spray bottle (let them know it contains a 50% Lysol solution) and cloth from the equipment table and begin to clean up their area.

Provide them with the following instructions:

Obtain a spray bottle and cloth from the equipment table. Wipe down your lab station and surrounding water fixtures and handles thoroughly. When you are finished, request an inspection with the “bacto-light”. Any missed areas will need to be re-cleaned! What areas did you miss? Where do you have to pay careful attention to next time? Students should respond to questions in their notebooks or journals and when they have successfully cleaned up their lab area, they can be checked off in their book.

Embedded Assessment

1. This exercise provides an opportunity to assess students’ pre-knowledge in their notebook responses and class discussion. Students’ ability to disinfect an area can be assessed through their practical application. Their understanding of why these procedures are important will be assessed later through their lab write-ups and responses to the embedded questions.