Lesson Plan

Introduction to Bacteria

Proof that Bacteria Inhabit Your Mouth
Terri E.
Classroom teacher
Creekland Middle School
Lawrenceville, GA
Show More
My Grades 6, 7, 8
My Subjects Science
Objectives

Students will be able to..

MS-LS-1  Conduct an investigation to provide evidence that living things are made of cells.

This will be accomplished by having students collect bacteria  from their mouths and  use a differential staining technique called, Gram Staining to show if the bacteria are gram positive or gram negative.

 

Subjects
Science
Grades 6 - 8
All Notes
Teacher Notes
Student Notes

1 Essential Question:EQ How can you prove that bacteria are present in your mouth?

BrainPop
From $220

Have students write the Essential Question: 

Agenda

EQ: How can you prove that bacteria are present in your mouth? 

Hook :Play "The Invisible World" clip from Youtube (3min 9sec) on microbes 

Discuss why its true that you are never truly along because of all of the bacteria and microbes constantly  living on your skin. (2min)

Ask the students to describe bacteria.  Allow them to work in groups for 2 minutes.  Have a spokes person from each group describe bacteria. 

Next  Ask students to take notes on the Brainpop presentation on Bacteria (4min 22 sec)

At the end students should have a:

1.  A definition of bacteria and at least 3 places bacteria can be found.  

2.  Students should also have 2 uses and  2 harmful affects of bacteria. 

3.  Shapes of bacteria

4.  Two main types of Bacteria 

Direct Instruction :Show ppt that outlines the 8 steps in the Gram Stain process  Give students a copy of directions or have them take notes over the powerpoint presentation

Be sure to explain the that a gram positive result is purple and a gram negative result is red/pink.  Show pictures of what gram positive and gram negative stains look like.

 Be sure to explain why lab technicians/scientists/doctors perform Gram  stain tests. Gram Staining is done  to distinguish between the various groups of bacteria and to prescribe the right medication to treat bacterial infections.

Materials: You will need : a bottle of Crystal violet,  95% alcohol solution, iodine, and Safranin red stain. Gram Stain kits can be purchased 1 kit usually contains enough materials for 50 students. Try Frey Scientific 

Two glass slides and cover slips per group of 2-3

Toothpicks 2-3 per group

Microscope 1 per group

Alcohol burner 1 per table

Latex gloves for all students

Clean-up - You will need a bucket and a bottle of rubbing alcohol. Have students place their used slides in and alcohol bath for 20 min rinse with water and allow to dry

Independent Lab work within groups-- Complete the Lab

Students should draw color pictures under showing what they have seen under medium power. Define Bacteria and state whether the bacteria are gram positive or gram negative. 

When students are finished have them place their slides and  cover slips into a bucket of rubbing alcohol.  Allow the slides to soak for 20 minutes then rinse with water and allow to dry

Wrap-up/ Summary- #STEMchallenge Ask students did they find bacteria and how do they know its bacteria?  Bacteria should appear purple.  If the specimens are red/pink it could be bacteria but likely they are cheek cells. 

Students should draw color pictures under showing what they have seen under medium power. Define Bacteria and state whether the bacteria are gram positive or gram negative.