Resource 22

Looking at microbes ¹

To look at microbes under the microscope, we first need to make some microbe food.

Hungry microbes!
Hungry microbes!

Collect:

  1. Boil the grass in some water for a few minutes. Leave it to cool to room temperature.
  2. Filter out the grass. The remaining greenish liquid makes great microbe food.
  3. Now add some microbes. Pond water is a good source of microbes, or you might be able to persuade your teacher to buy a paramecium (para-mee-cee-um) culture from a biological supplier. Add a few drops to your green liquid.
  4. Leave the liquid for a few days until the microbes grow.
  5. Make a slide from a drop of the liquid and have a look at it down the microscope.
  6. Draw what you see.

Questions

  1. Melbourne Water want to extend their land filtration area into some paddocks which have a heavy clay soil. If you were an engineer advising them, what would your advice be? Give some reasons, using the evidence from your experiment.
  2. Some school aquariums have under-gravel filters. Water is drawn into the gravel at the bottom of the tank, taking with it fish wastes and uneaten food. The wastes are broken down in the gravel. How does this happen?
  3. Why is it important not to put poisonous substances down the toilet?
  4. Draw a flow chart showing how sewage is treated at the Western Treatment Plant.

Extension - Feeding microbes

A good experiment to try is to feed some microbes and watch what happens to the amount of oxygen.

  1. Add a spoonful of yeast (yeast is a microbe) to a conical flask.
  2. Add some sugar, some water and a few drops of methylene blue - enough to get a blue colour.
  3. Stopper the flask and leave it for a few days.
  4. As the microbes grow, they use up oxygen and, as the oxygen is used up, the methylene blue should lose its colour.

In the first lagoons at the Western Treatment Plant, fast microbe growth uses up almost all the oxygen, resulting in the water becoming smelly.

¹ Based on an activity from: Keith McTaggart and Paul Saddler 1993, Flushing Dunnies, Melbourne Water and Science Teachers Association of Victoria.