Ultra-violet radiations prevent the production of red pigment, Prodigiosin in Serratia marcescens by inducing mutation in its DNA.
Hypothesis.
Maybe the disappearance of red color in serratia marcescens is caused by the UV light which causes mutations in its DNA.
Prediction.
If UV light mutates the DNA producing prodigiosin, then red colonies of bacteria will no longer be produced.
Independent.
Ultraviolet radiations (placed on four quadrant of petri dish, with exposure to each quadrant of 10's, 20's, 30's, 40's).
Dependent.
Color change and survival of Serratia marcescens.
Control.
Nutrient agar plate with streaks of Serratia marcescens without UV light.
Results.
S.marcescens is a gram negative rod shaped bacteria, containing pigment prodigiosin. The control group after incubating at 25 degree Celsius, showed the growth of red colonies. It proves that it contains normal (red) strains of S. marcescens.The experimental group with lid on it also showed the growth of red colonies, similar to the control. The lid protects the bacterial DNA from damaging by UV light. Comparatively, the experimental group exposed to UV light showed significant change. The quadrant of petri dish exposed to 10s contained red colonies. The one exposed to 20s showed disappearance of red colonies and subsequent formation of white colonies. The third quadrant, exposed to 30s showed significant reduction in the red color with white colonies overlapping it. Finally, the fourth quadrant showed very spots of red color, indicating that the majority of bacteria have died on exposure to UV light.
Exposure Time.
10.
sec.
20.
sec.
30.
sec.
40.
sec.
Control - UV.
The red colonies are formed.
Control+UV,+lid.
The lid protects the bacteria. Thus red colonies are formed.
Red colonies are formed.
Experiment+UV.
Red colonies are formed regardless of the exposure to 10s UV light.
Red colonies starts to disappearing.
Significant reduction in red colonies. Bacteria starts dying and white colonies are forming.