BACTERIA GROWTH
Background:
We are testing to see what growing conditions are best for growing bacteria. We are doing this because we are interested in doing this experiment because we want to predict what kinds of places would have the most bacteria. Bacterial growth of the population is a geometric progression of numbers of cells, with division occurring in regular intervals, called generation time, ranging from 15 minutes to 16 hours, depending upon the type of bacterium. In addition, some filamentous bacteria (actinomycetes) reproduce by producing chains of spores at their tips, while other filamentous species fragment into new cells. In general, the physical requirements for bacteria include proper temperature, pH, and osmotic pressure. Most bacteria thrive only within narrow ranges of these conditions, however extreme those ranges may be.The lowest temperature at which a particular species will grow is the minimum growth temperature, while the maximum growth temperature is the highest temperature at which they will grow. The temperature at which their growth is optimal is called the optimum growth temperature. To do a proper experiment, we will need to know what will help the bacteria grow and what the controsl will be. We will need to know how bacteria actually grow also to help with the experiment.

Procedure.
We are going to set up three petri disheswith agar in them and have them in four different places. After pressing my finger into the agar we will place them in the following places. One will be in a dark place such as a cabinet. The second one will be set under a heat light. And the last one will be at room temperature in an open room. We will graph our data every week day for about two weeks.

Materials:
  • Petri Dishes
  • Source of bacteria
  • Heat Light
  • Dark, Secluded Place

Hypothesis.
If we leave the bacteria in a dark place with no light, then It will grow more bacteria than our control.
If we leave the bacteria under a heat light, It will grow less bacteria than our control.

Data:


Amount
Of
Bacteria




Location
Day 0
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Under Light
0 cm.
15 cm.
17 cm.
20 cm.
23 cm.
23 cm.
23 cm.
23 cm.
In Drawer
0 cm.
4 cm.
7 cm.
10 cm.
10 cm.
11 cm.
11 cm.
11 cm.
On Counter
0 cm.
10 cm.
17 cm.
19 cm.
20 cm.
20 cm.
22 cm.
22 cm.






Analysis:
The data that we have gathered shows the following.The petri dish that was on the counter was our control. It grew pretty rapidly and had a great deal of bacteria in it at the end of of the experiment and towards the beginning of the experiment. It stopped producing bacteria and basically stayed the same after day 5 or day 6. It had a total amount of bacteria equalling 22 cubic centimeters at the end of our experiment. Our second petri dish was exposed to a light. This light is the same light that is used to help our plants grow in other class room experiments. This petri dish produced just a slight bit more bacteria than our control petri dish that was exposed to just everyday light. It started off having 15 cm. after the first day. It did not stop there. It kept growing and growing producing more bacteria each day. It stopped growing or maxed out after day 4. The final amount of bacteria in that petri dish was 23 cubic centimeters. Our third and final petri dish was placed in a dark drawer and was exposed to only the light that it received when I measured the amount of bacteria that was in it. This petri dish grew the least amount of bacteria. After day one it was over 5 cm, behind the other two petri dishes. It stayed behind them the whole experiment and ended up with a total amount of bacteria equalling 11 cubic centimeters. From this data, we were able to find out that the heat light actually did cause the bacteria to grow the most. The control grew about how much we expected. And the petri dish that was in the drawer grew the least, which was what we expected to happen. The control and the petri dish in under the heat light were very similar in growth leading us to believe that heat can effect bacteria growth, but it does not make too much of a difference in growth. I think that the small differene in growth was by chance since the two results were so close together.

Conclusion: From our data, we can conclude that bacteria that does not receive light, will indeed not grow as fast and will not produce as much bacteria as bacteria that is exposed to light. Our results did not support our hypthesis, becasuse the control grew more bacteria than than the petri dish in the drawer, and grew less than the petri dish that was under the light.

Limitations: From our experiments, we could have had one major human error, contamination. When we prepared the petri dish, it is possible that we let other bacteria that we didn't intend to have inside the petri dish. We also could have made the mistake of not properly sealing the petri dish, which would have allowed bacteria that was either floating or being pushed by the wind to land inside of the petri dish. Both of these issues could have been solved by being more careful while preparing the petri dish and when applying bacteria to them.


Sources:
"Bacteria." The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Vol. 1. Detroit: Gale, 2008. 439-447. Gale Virtual Reference Library. Web. 30 Nov. 2012.

"Bacteria Divide and Multiply." Bacterial Growth and Multiplication. N.p., n.d. Web. 06 Feb. 2013.

"Factors That Influence Bacterial Growth." Factors That Influence Bacterial Growth. N.p., n.d. Web. 06 Feb. 2013.

Todar, Kenneth, PhD. "Growth of Bacterial Populations." Growth of Bacterial Populations. Kenneth Todar PhD, n.d. Web. 06 Feb. 2013.