Vineeta Singh's Bacteria Page


Bacteria Page



This nutrient broth was kept in my patio. While it is outside, it is usually closed and maintains a temperature from 70-75o
F. During the time period that this experiment was being conducted (September 2015) the weather  was especially hot so it may have gotten as hot as 80o F. On the first day the plate was exposed for 10 minutes. Everyday after that it was exposed for 1 minute at about 7:00 AM.

Results 1. Area of the Plate Covered by Bacteria
Table 1. Percent of Area of Plate that is Covered by Bacteria
 Day Percent of Plate Covered by Bacteria
 1 0
 2 0.05
 3 31.73
 4 58.53
 5 95.00
 6 97.15
 7 97.28
 8 97.53
 9 98.00
 10 98.11
 11 98.15
 12 98.45
 13 98.47
 14 98.60
 15 99.13
Figure 1. Graph of Table 1.

Results 2: Individual Colony Growth
  Type 1
(Green)
 Type 2
(Black)
 Type 3
(White)
 Type 4
(Brown)
Day 1
 0 0 0 0
 Day 2
 0 0 2 0
 Day 3
 4 0 11 0
 Day 4
 7 3 15 1
 Day 5
 0 5 10 5
 Day 6
 0 5 15 6
 Day 7
 0 7 9 14
 Day 8
 0 10 14 14
 Day 9
 0 9 12 10
 Day 10
 0 10 13 11
 Day 11
 0 14 9 17
 Day 12
 0 15 7 24
 Day 13
 0 12 7 24
 Day 14
 0 10 7 24
 Day 15
 0 14 8 21
Figure 2. Graph of Table 2

Conclusion
My bacteria plate is a perfect example of logistic growth. In the first 4 or 5 days the bacteria grew a lot. After this time period it continued to grow but not as fast. This is probably because all the nutrients in the agar were absorbed within the first couple of days. This idea is best shown in the first way that I analyzed my results. The first way was done my using imagej to calculate the area of the entire plate, then calculating the area covered by bacteria, then dividing to find the percent of the plate covered by bacteria. As you can see it only took 5 days for the bacteria to grow and cover 95% of the plate. After that it continued to grow but at a very slow rate. In the first 5 days it went from 0 to 95 and in the next 10 days it only went from 95%-99%. This shows that as the nutrients were being used up, the rate of growth decreased dramatically. In the second way I analyzed my data, I counted the types of colonies that were growing and hoe many were present in my plates each day. They usually increased. I suspect that some of the colonies decreased because they turned into other colonies. For example the green colonies (Type 1) were soon replaced by the black colonies (Type 2). My colonies were very large and very colorful.
What I Learned:
From this project I learned many things. I learned that concepts such as logistic growth and carrying capacity can be applied not only on large scales such as with humans and animals but also on extremely small scales such as with the bacteria. I know that the bacteria grew as much as it could have given the resources it was given. If it had been given more room or more nutrients it would have continued to grow until it reached the carrying capacity of the new environment. Another thing that I have learned is that bacteria of many different shapes and sizes can grow from the same environment.

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