Chris Park Bacteria

I started on September 17 and first exposed it into my room on my windowsill. During that time , the weather was extremely hot and my window was open. The petri-dish was left in my room and didnt leave. The temperature was moderately hot and warm during the day and cool during the night. My house does not have an AC. Starting from Sept 20, i am unable to open the petri dish as the bacteria started to grow onto the top lid. I noticed in the morning they get their water from the condensation on the inside of the lid. My type is MM.

Growth of Bacteria and Fungus Experiment

Results#1: Total Area of the Colony.

total area of the colony

Result #2: Number of Colony. 

Number of Colony


My bacteria colony in the plate is one example of a logistic growth of an environment. The first 2 days there was nothing but starting from the 3rd day, small bacteria and fungi began to grow. The suddenly from day 3 to 4, there was a dramatic change. The bacteria and especially fungi grew instantly overnight. This is most likely due to all the nutrients being absorbed and growing more. 

Starting from day 7, there was a decrease in slope. And from there, the number of colonies and the total area of the colony increased and decreased over and over, due to the carrying capacity. The carrying capacity was mostly the amount of resource (food) and amount of space in the small petri dish. I analyzed my data using imagej to calculate the area used by the colonies each day and in comparison to the area of the petri dish. by the 4th day, the bacteria covered, 61.43% of the dish. From days, 9-17 the area percentage decreased and increased at a slow rate between, 61.43% - 97.70%. Then from day 7 to day 11, there was an decrease of the number of colonies but an increase of the total area used by certain bacterias and fungi from day 7 to 9, showing natural selection of the environment within the petri dish: the bacteria that were more suited for the survival survived while other weaker organisms died off. 

The second results I analyzed from counting the number of colonies there were each day. The lowest number of colonies was 8 on days 11, 14, 15 and the highest number of colonies was 12 between days 6-7. There was an increase due to new colonies growing and eating off the food, and there was a decrease of colonies due to other colonies stealing resources and the weaker colonies dying off. 

What I Learned

From this experiment we can learn and understand the aspect of logistic growth, carrying capacity and natural selection. These concepts work on any population, in any environment, including the small scale of bacteria and fungi in a petri dish. The maximum number of colonies and total area used were limited by the carrying capacity of the environment. If the environment had more food, resources and much more space available, then the resulting numbers of the total area consumed by the bacteria and fungi would differ and reach a new higher carrying capacity. The number of colonies, though, would differ as several colonies might consume more space and resources and survive, and so there could be less amounts of colonies if the carrying capacity was increased.