Bacteria Growth

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Bacteria are a specific kind of prokaryotic organisms that are very versatile and can survive in many different environments and can be found practically anywhere. Bacteria can be of existence in three distinct shapes: bacillus (rod-shaped), coccus (spherical),), and spirillum. It can reproduce and change in many ways. Some of the ways it reproduces are through binary fusion, the transferring of genetic material and spores.

While it is effortless to think of pathogenic bacteria (disease causing) and the harmful effects it contributes to our body. Many times, people neglect to think about how bacteria are beneficial and essential to human life. Many of the bacteria in our bodies play an important role in human survival. Bacteria in the digestive system break down nutrients, such as complex sugars, into forms our body can use. Non-hazardous bacteria also help prevent diseases by occupying places that the pathogenic, or disease-causing, bacteria want to attach to. Some bacteria protect us from disease by attacking the pathogens.

To learn more about techniques involved in studying bacteria, we took several cultures from different doorknobs found in the Coastal Community College Health Building in the back staircase to see which doorknob would carry the most bacteria. We hypothesized that the doorknob(s) used to go into the building would hold the most bacteria compared to the other knobs used going out. Our reason imagined because people show up to class at different times might would result in the knob being touched or used more. Whereas when classes are letting out you usually see one student holding the door with their hand or kicking it open, elbowing it etc., for the other students as they leave the building.

Materials and Methods

  • 1 Petri dish, prefilled with agar
  • 2 packs of cotton swabs, containing two cotton swabs in each package
  • 1 black sharpie marker

We were given an already prepared agar-filled petri dish. Also, 4 cotton swabs (two packs), and a marker used for labeling the dish. After becoming familiarized with the techniques used to culture bacteria, we set out to test our hypothesis. First, reminding us to divide the bottom part into 4 halves. Specifically, the bottom since the top can rotate, we didn’t want to get confused. We labeled the bottom of the dish as followed; TD1, TD2, BD1, BD2. (Top Door 1 and 2, Bottom Door 1 and 2)

Top door one (1) stands for going out and top door two (2) represented going in. We started at the top part of the stairs. Taking a cotton swab out of the packet rolling it across the surface on TD1 knob (going out) and then rolling it across the agar in its designated spot in the dish. Disposed of the swab and repeated the same steps for other side of TD2 knob (coming in).

We then made our way to the bottom of the staircase and repeated the same steps as mentioned before with TD1 and TD. Bottom door one represented going out and bottom door 2 represented going in. We started with bottom door 1 (BD1) going out and then repeated the same method on BD2. We made our way back up to our classroom and disposed of cotton swabs, handed over our dish and our teacher then incubated it for I am assuming about a week.


Located on doorknob number 2 at the bottom of the stairs, going out is where the sample that bacteria multiplied from came from. Each bacterium consists of a tiny cell that must be magnified at least 400 times to be visible. Even though individual cells are not visible without the aid of a microscope, bacterial colonies (clumps of bacteria) grow large enough to be seen clearly. Based on the picture only, without the aid of a microscope it appeared to be white. I cannot describe in detail shape, other than it appearing to be round. Nor can I describe the exact texture, such as if its fuzzy, or porous, etc., I don’t know how this knob had more bacteria on it then the other knobs or any of the knobs for that matter. Pictured below is the physical result.


Even though the results were nowhere near our hypothesis. Which resulted in us being wrong. We still were able to collect and see some colony formation of bacteria in the staircase found in the Coastal Community Colleges Health Building. In this lab we have focused on bacteria growing and seeing the growth of bacteria in favorable condition as well as the observation of the color of the bacterial colony. We hypothesized that the doors used going in would hold more bacteria as to the doors going out. Bacteria are found in a wide variety of environments – in or on animals and plants, in water, in soil, in air, or on rock.

Generally, they are contributors to the environment, decaying nutrients and recycling the minerals (for use by plants and other organisms). Bacteria are both metabolically diverse as well as structurally diverse. As I have learned we carry bacteria when we are in perfect health as well when we are sick. From this lab we have learned that bacteria are present everywhere, but we can achieve a healthy life by maintaining good hygiene. We gained valuable experience in culturing and applying the culture onto the sample.

Maybe in the future we can use it with our children and be a little more precise or in fact. We might have taken into consideration that the janitor had been upstairs and maybe she was cleaning and had already wiped down the knobs of the doors found at the top of the stairs. She was in fact in the hallway that morning. Another problem could’ve been the way we swiped the swabs across the agar. I twisted it between my fingers rolling around back and forth and maybe this then made it wipe back off the agar, onto the swab. I don’t know for sure; I am only saying as to maybe why there was no other bacteria in the other panels


Cite this paper

Bacteria Growth. (2021, Aug 24). Retrieved from https://samploon.com/bacteria-growth/

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