Daiwei (David) Lu-Bacterial/Fungal Growth Page

This nutrient broth plate was exposed for 10 minutes to the atmosphere in my bedroom.
It is kept in relatively warm temperatures during the day until around 5:00 PM when the air conditioner is turned on and the temperature is maintained at around 75 degrees Fahrenheit.  The air conditioner is turned off at around 7:30 AM each day.

Bacterial/Fungal Growth

ImageJ Screen Captures


My nutrient broth plate was exposed for ten minutes to the atmosphere in my room.  It was then closed and left upon my desk with little to no exposure to natural sunlight.  For the first week, the bacteria grew quickly, establishing many colonies.  Growth of new colonies soon slowed down.  Additionally, the further growth of already existing colonies slowed down.  ImageJ was used to obtain accurate counts of the amount of bacterial colonies growing.  I hypothesize that because the nutrients and water content in the nutrient broth agar was being used up, the further growth of colonies was limited.  This is an example of logistical growth, with the bacterial growth slowing down as resources are used up and the carrying capacity being approached. 
None of the colonies grew to a very large size.  Additionally the colonies were randomly distributed on the plate, but did not cover the entire plate.  I hypothesize that this is due to the colonies drawing from not only the agar it is directly over, but surrounding it as well.  It must be noted that on Day 8, the plate was accidentally opened by my sister, possibly causing a disturbance in what would have been the normal logistic growth. 

As the plate was subjected to a constantly changing environment, it would be useful to set up a separate plate unexposed to the atmosphere as a control.  This excludes the growth of bacteria on an unexposed plate due to conditions such as less than optimal sterilizing conditions. 

What I've Learned

I have learned that, though miniscule in size, bacteria and fungi are still affected by carrying capacity and logistical growth patterns.  They cannot grow unrestrained and exponentially for very long before exhausting available resources.  If there was an increased amount of agar to grow, then the growth of the colonies would be much greater and could show additional events that occur as a part of logistic growth, such as colonies competing for space.