Students participated in a variety of activities to demonstrate how small individual bacteria and yeast are:
1) Students saw an image of bacteria on the tip of a pin at several levels of magnification. The purpose was to provide a context for understanding the size of the bacteria.
2) Students discussed the need for a smaller unit of measurement. For measuring bacteria and yeast, micrometers ( m m) were proposed by the teacher. Students were asked to think about the size of a meter and were told there are 1000 millimeters in a meter. There are 1000 m m in 1 mm. Then, knowing the average size of a bacteria cell (10 m m) and a yeast cell (100 m m), students could begin to comprehend how microscopic these organisms are.
3) Students made slides of the microbes (bacteria and yeast) from colonies on agar plates. While looking at the slides under increasing magnification, students drew the shape and relative size of each organism. The yeast are clearly visible (detail of individual cell) at 400X. The bacteria are too small to see with the 400X magnification, but they can be seen with a 1000X oil immersion scope.
