Cultivation of bacteria found on disposable cups.

Teachers-In-Charge:Miss Yong Ren Cui:Mrs. Choy Hui Peng

Group Members:Alayne Loo:Esther Ou:Lee Si Ting:Pang Hui Xia

OBJECTIVE

To investigate and find out which type of disposable cup material attracts and collects the most bacteria.

HYPOTHESIS

A disposable cup made of styrofoam collects the most bacteria.

Materials.•Ingredients : LB medium powder (7.5g x 2) : Agar-agar powder (2.4g x 2) : Water (300ml x 2) •Equipment: Horizontal laminar cabinet: Refrigerator: Autoclave : Microwave oven: 21 petri dishes (100 x 15 mm) : Glass rod: Glass bottles: Ethanol: Disposable gloves: Bleach•Materials used for bacteria growth: Styrofoam: Plastic: Paper: Microscope slide cover slips

Cut 2cm x 2cm of each material without tearing the agar surface, and inoculate the dish by pressing each material on a separate petri dish.

Label the petri dishes, and seal them with Parafilm and store upside down.Let bacteria grow in an undisturbed location, and bacteria growth should be observed within the next few days.Before disposing of dishes in the trash the bacteria should be destroyed. Pour a small amount of household bleach over the colonies while holding dish over sink. (Caution - do not allow bleach to touch your skin, eyes or clothes. It will burn!)

Type of disposable cup used

Amount of bacteria collectedLow Moderat

eHigh

Plastic √

Styrofoam √

Paper √

Paper

Styrofoam

Plastic

0 2 4 6 8 10 12 14 16 18 20

Base

Side

results

Area of bacteria colonies (cm square)

Discussion.

The outcome of the experiment is such that: •Paper cups collect the most bacteria, followed by styrofoam and then plastic respectively. • Paper cups collect the most bacteria as it is a natural substance made of pressed cellulose pulp derived from wood, rags or grasses, whereas plastic and styrofoam are both man-made materials. • This is why bacteria is most attracted to it as it can then feed on the natural fibres of the paper, plus, paper is biodegradable too.• Styrofoam had a significant amount of bacteria too, though not comparable to paper, as styrofoam is a type of extruded polystyrene foam where there are many holes and air spaces allowing bacteria growth in them. • Plastic is a smooth man-made material, thus bacteria found on it is mainly from the atmosphere or bacteria from the things that come in contact with it like e.g. our hands, tabletops, tissue etc.

Conclusion:• Through our control experiment, we have discovered that re-usable melamine cups attract and collect very little bacteria compared to the three disposable cups, plus it is also more environmentally friendly and cheaper too. • The paper production can cause almost twice as much CO2 emissions and energy consumption as creating plastic or styrofoam products. • Some paper cups are also not recyclable if they have a wax coating on them. • Producing paper cups can also take more material by weight to produce for proper insulation compared to styrofoam and plastic cups.• Styrofoam cups can insulate very well but they can break into small pieces that can be bad for children and animals. Styrofoam is created from benzene and other chemicals that can be bad for you and contribute to smog and global warming. • Plastic also produces chlorofluorocarbons which destroys our ozone layer and contributes to global warming and it is also not biodegradable, making it an un-environmentally friendly choice of disposable cup to use, • Therefore we encourage everyone here to use re-usable mugs.

THANK YOU!!