Purpose: In this lab you will explore the three basic shapes of bacteria. Although there are more than 3 shapes of bacteria, we will observe the 3 most common. We will do this by exploring bacteria in yogurt.

Download the copy of this lab sheet for this activity.

Bacteria have three basic shapes.
 - Bacilli, or rod-shaped
 - Cocci, or sphere-shaped
 - Spirilla, or spiral shaped

Bacteria can also arrange themselves into colonies. Each arrangement is given a special name.
 - (prefix) Diplo-, meaning paired (ex: diplococcus, a pair of sphere-shaped bacteria)
 - (prefix) Strepto-, meaning chain (ex: streptobacilli, a chain of rod-shaped bacteria)
 - Tetrad, meaning group of four (note: this is not a prefix. You would just say "tetrad cocci bacteria")
 - (prefix) Staphylo-, meaning random (ex: staphylococcus, a random arrangement of sphere-shaped bacteria)

Scientists and doctors can identify bacteria by their shape and arrangement. For example, if you've ever had strep throat, the doctor probably took a sample from your mouth or throat. They are looking for bacteria that are spherical and in chains. The technical name of this is streptococcus. Hence the name: strep throat.

For each picture below, indicate the bacterial shape.

Picture 1:
Which shape does this picture show:
Bacilli, Cocci, or Spirilla?

Picture 2:
Which shape does this picture show:
Bacilli, Cocci, or Spirilla?

Picture 3:
Which shape does this picture show:
Bacilli, Cocci, or Spirilla?

Picture 1:
Which arrangement does this show?
Diplo, strepto, or tetrad?

Picture 2:
Which arrangement does this show?
Diplo, strepto, or tetrad?

Picture 3:
Which arrangement does this show?
Diplo, strepto, or tetrad?

Below is a picture of bacteria found in yogurt. Draw three different bacteria and indicate their shape. For example, you might find a chain of rod-shaped bacteria. You would draw them and then say they are "streptobacilli."

In lab 1 from unit 9 you drew pictures of three cyanobacteria. Look at your pictures of merismopedia and anabaena. What are their shapes (bacilli, cocci, or spirilla)? What are their arrangements (diplo-, strepto-, or tetrad)? For reference the pictures have been included below.