Survey of Bacteria and Moulds around the school, and

Authors Avatar

Survey of Bacteria and Moulds around the school, and the cleaning techniques used.

Research Questions:

  1. Which types of floor surface around the school will harbour the most mould and bacteria spores?
  2. Which cleaning regimes used on these different surfaces are most effective?


  1. Those floor surfaces that are made of concrete, tiles, rubber or linoleum will harbour fewer bacteria and mould spores than those surfaces which are carpeted.
  2. Surfaces which are cleaned more regularly will harbour fewer bacteria and mould spores than those that are cleaned less regularly.


        Independent Variables:

  • Type of floor surface
  • Regularity of cleaning
  • Cleaning products used

Dependent Variable: Amount of bacteria and mould spoors present on the floor surface and in the surrounding atmosphere.

Controlled Variables:

  • Amount of time petrie dishes are left open
  • Amount of time mould and bacteria are left to grow
  • Temperature of storage of dishes for mould and bacteria growth
  • Day of the week that dishes are set out
  • Time of day that dishes are set out


  • Petrie dishes
  • Stop-watch/timer
  • Incubator
  • Sticky tape
  • Sticky labels


  1. Select twelve different rooms around the school, plus one location which is outdoors as the control location.
  2. Label two petrie dishes with each location, using the sticky labels. Only one dish is required for the control location.
  3. On a Friday morning, between 8:45 and 10:45am, we took the petrie dishes to the different locations around the school.
  4. In each location, we set two petrie dishes on the floor side by side, and removed the lids. We allowed the dishes to sit with their lids off for four minutes, after which time we replaced the lids. We made sure that we stood back from the dishes once we had placed them on the floor, so that particles did not fall from us into the dishes. We also made sure that the dishes were in a part of the room where they would not be stepped on, and also where there were not too many people waking past very close to them, so that particles would not fall from the people into the dishes.
  5. After replacing the lids on the dishes, we taped the dishes closed with sticky tape.
  6. Once all the dishes had been exposed, we took them and placed them in the incubator.
  7. The moulds and bacteria were allowed to grow for three days. On Monday morning, we took them out of the incubator and counted the number of mould and bacteria colonies in each dish.


Table 1: raw data

Join now!

Table 2: standard error of means

Although it is not normally reliable to calculate the standard error using only two samples, these have been included in order to illustrate that the variation in the readings at sites is less than the variation in the readings between sites. This shows that the site means can be sensibly compared.

Figure 1

series 1 = mould colonies – dish 1

series 2 = bacteria colonies – dish 1

series 3 = mould colonies – dish 2

series 4 = bacteria colonies – dish 2

As we can ...

This is a preview of the whole essay