Escherichia Coli and Staphylococcus Albus

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Escherichia coli and Staphylococcus albus

Some bacteria's require a certain amount of light in order to function properly and there fore survive. Escherichia coli is found in the gut and intestines of mammals. Staphylococcus albus is generally a skin dwelling bacteria

Aim: To test whether the amount and type of light that the bacteria's E.coli and S.albus are subject to causes changes in their growth rates and habits.

To test whether the growth rates and habits of the bacteria's E. coli and S. albus are subject to change when to a varying amount and type of light.

Hypothesis: that the different types of light will affect the growth rate of the bacteria's. From prior knowledge and assumption of the environment, it is believed that higher temperatures will assist in the growth rate in the agar plates. Therefore it is believed that the agar plates placed in full light will produce more bacteria. Due to the type of light used for the full light part of the experiment there will be higher temperatures and therefore grow better than the no light and day light plates which are at lower temperatures.

Equipment and Materials:
16 agar plates
2E. coli and S. albus bacteria
4Day light
8Adhesive tape

1.using three agar plates make a lawn culture with E.coli, do the same with the other three agar plates with S.albus. 2.Separate into the following groups
i.E.coli (1)
ii.S.albus (2)
-No light
i.E.coli (3)
ii.S.albus (4)
-Full light
i.E.coli (5)
ii.S.albus (6)
3.Place all plates in cupboard and incubate for 3 days undisturbed.

4.Place each pair of plates in the appropriate location
-Full light in an area that allows it to be in constant effect of the light and undisturbed with the exception of the data recording
-No light in an area which allows it to be in almost constant complete darkness and undisturbed with exception of data recording
-Day light in an area, which allows it to be in an almost naturally occurring situation, as this is the control.

5.Check and record progress every two days

Results and Observations:

All plates set up as described in step 3 of method and left for 3 days

Observed a thin film of bacteria on each dish and each pair was placed in the appropriate location as specified in step 4 of method and left for 2 days

Plates 1 and 2 from the day light pair have a small amount of condensation on the lids. Both plates have continued bacterial growth. On the agar small white dots have formed, more occurring on the S.albus plate than the E.coli. This evidence suggests that since there are more introduced bacteria growing on the S.albus plate.

Plates 3 and 4 have almost no change to bacterial growth with exception of a spread of small white dots of alien bacteria on the S.albus, which was also found on subject 2.

Full light has sustained heavy condensation due to the increased temperature compared to that of the other subject's environments. The condensation appears to be collecting and then dropping back down onto the bacteria thus washing it around the plate. In this pair the E.coli has sustained an alien bacteria rather than the S.albus. The alien bacterium is yellowish in colour and forms striations.

Daylight - E.coli – condensation on the lid and dots of foreign bacteria, yellow and pink in appearance.
S.albus – even spread of small white dots

No light – E.coli – no change
S.albus – small white and translucent dots

Full light – heavy condensation on the both. Condensation from the lid falling onto the agar has cased the bacteria to be washed around the plate. But there is a better overall growth for the E.coli

Daylight – E.coli – increased growth on white dots, no change in condensation.
S.albus – overall increase in the spread and size of dots

No light – E.coli – no change
S.albus – no change...
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