The effect of temperature on the growth of microorganisms

Aim: To study the effect of t............................. on..t.....................................

Problem Statement: How does ...t.................affect ...t......................................?

Hypothesis: Bacteria grow well in the temperature of 37 C

Variables:

- Manipulated Variable:T.........- Responding Variable: G.................o............ m- Fixed Variable:Light intensity, humidity, pH, the amount and type of temperature

Materials: Nutrient agar, culture of bacteria ( Bacillus subtilis), cellophane tape

Apparatus: Petri dish, oven

Procedure:

Diagram* refer the whiteboard

1. The Petri dishes containing nutrient agar are labelled as A and B2. 1cm 3 of bacteria culture is poured onto the agar in each Petri dish.3. The Petri dishes is covered and sealed with cellophane tape.4. The Petri dish is overturned.5. Set A is put in a refrigerator.6. Set B is placed in an oven at a temperature of 37C

7. After two days, the petri dishes are taken out. The appearance of nutrient agar in each Petri dish is observed and recorded.

Result:

Petri dish A BLocationTemperatureObservation

Discussion:

1

The effect of pH on the growth of microorganisms

Aim: To study the effect of ............................. on.......................................

Problem Statement: How Does ....................affect .........................................?

Hypothesis: Bacteria grow well in neutral medium

Variables:

- Manipulated Variable:p.........- Responding Variable: G.................o............ m- Fixed Variable:Light intensity, humidity, temperature, the amount and type of

temperature

Materials: Nutrient agar, culture of bacteria ( Bacillus subilis), cellophane tape, hydrochloric acid and sodium hydroxide

Apparatus: Petri dish,

Procedure:

Diagram* refer the whiteboard

1. The Petri dishes containing nutrient agar are labelled as A and B2. Five drop of hydrochloric acid is added to Set A3. Five drop of sodium hydroxide are added to Set B4. Five drop of distilled water are added to Set C5. 1cm 3 of bacteria culture is poured onto the agar in each Petri dish.6. The Petri dishes is covered and sealed with cellophane tape.7. The Petri dish is overturned.8. Set A is put in a refrigerator.9. Set B is placed in an oven at a temperature of 37C

10. After two days, the petri dishes are taken out. The appearance of nutrient agar in each Petri dish is observed and recorded.

Result:

Petri dish Conditions of nutrient agar Observation of the nutrient agar

A AcidB AlkalineC Neutral

Discussion:

1. Bacteria grow well in neutral conditions. Hence they are many white spots which are colonies on the nutrients

2. Condition that are too acidic or alkaline is not suitable for bacterial growth.3. Hypothesis is accepted

Conclusion:

Bacteria grows rapidly in neutral condition.

Aim : To study the effect of humidity on the growth of microorganisms

Hypothesis : Microorganisms grow rapidly in m....... condition

Variables : Constant : Type of b....../ t............/ nutrient content Manipulated : Presence of w...... Responding :The g....... of microorganisms /mucor/fungi

Materials/Apparatus

: 2 pieces of bread, water, clear plastic bag.

Procedure : 1. A piece of bread is sprinkled with water and placed in a clear plastic bag labeled A.

2. The other piece is kept dry and placed in the clear plastic bag labeled B.

3. Both plastic bags are kept in a dark cupboard for two days.4. The result of the experiment is observed and recorded in

the table below.

Results :Presence of moisture The growth of mucorA Moist bread Yes / A lot of mucorB Dry bread No / A few mucor

Data interpretation and discussion

: After two days the mucor grows on the moist bread because of the presence of water but no mucor grows on the dry bread. Mucor needs water to grow. Hypothesis is accepted.

Conclusion : Microorganisms grow rapidly in m....... condition

C1 P2

C1 P3Note: All variables must be correct

C1 P4

B: Dry bread A: Moist bread

Plastic bag

C1 P5C3 P1

C3 P2

C3 P3

C4 P1

C4 P2

C4 P3