Sample Biology Lab

Introduction:
Living, microscopic, unicellular organisms can be identified as microorganisms. Fungi, Protista, Bacteria, and Archaeans are four kingdoms in the phylogenetic tree of life that consist of microorganisms. Amongst these microorganisms the prokaryotes were the first ones to arrive through evolution. The rest of the life forms as we see them evolved from these simple creatures, prokaryotes. The smaller prokaryotes were swallowed by bigger prokaryotes setting the stage for the origin of eukaryotes. These eukaryotes then evolved into protists, fungi, plants, and animals. As they evolved, so did the way they reproduce. From simple asexual reproduction (binary fission) to sexual reproduction thereby expanding the diversity of the life
form. Along with the diversity came their ability to survive in diverse environment ranging from hot thermals to freezing ice caps. There is strength in unity; the unicellular organisms thrived in a colony form of living.
The purpose of this experiment was to investigate the diversity and population density of bacteria at four different locations.
Four locations frequented by the school populace were selected, they included; the handle of the paper dispenser in the first floor women's restroom, the spatula used in the sandwich bar in the dining commons, the outer handle of the front entrance to the Upper School, and the microphone part of the podium. The plan was to collect samples of the bacteria with the help of a swab and transfer them to individual Petri dishes at the same time to prevent any variability in the experiment. The bacterial samples would be allowed to grow in an agar medium under the same conditions. The colonies were allowed to grow for a certain period of time before emulating their growth pattern and appearance. In this experiment the independent variable is the location and the dependent variable is the growth
pattern.
The bacterial growth pattern depends on the frequency of exposure by the students to the chosen locations. Based on this criterion, the outer handle of the front entrance door will have the highest growth pattern. Because that is the main point of entrance into the building, it is expected that it will have the densest bacterial colony and diversity of bacteria.
Methods:
I procured one Petri dish, marked into four quadrants for the four locations, containing the growth medium and swabs to lift the bacteria from these locations. Samples were collected by rubbing the swab onto the location of interest and then transferring it onto the Petri dish by gently apply it to the appropriate quadrant. Quadrant A = the handle of the paper dispenser in the first floor women's restroom, Quadrant B = the spatula used in the sandwich bar in the dining commons, Quadrant C = the outer handle of the front entrance to the Upper School, Quadrant D = the microphone part of the podium. The Petri dish was immediately covered to prevent any contamination and the swabs were discarded. The covered Petri dish was placed in a dark incubator of 37 degrees Celsius. The bacterial colonies were allowed to grow uninterrupted for a period of X days. At the end of the period, the Petri dish was removed form the incubator and promptly analyzed by visible means and the observations were recorded, tabulated, and graphed.

Results: Visual analysis of the four quadrants showed that the densest bacterial growth was in quadrant C and the spatula handle in quadrant B showed relatively the least amount of growth. Quadrant D (microphone handle of the podium) had a higher growth than quadrant A (the first floor women’s bathroom’s paper dispenser handle). In other words, the increasing order of bacterial growth in the four locations is B, A, D, and then C.
Discussion:
The findings of the experiment support our initial hypothesis that the most frequented location (the handle of the front door entrance to the school) would have the greatest bacterial population.
The quadrant representing the handle of the front door entrance to the school had uniformly dense growth. In contrast, the other quadrants had spotty growth. The results are also summarized in the graph and can be seen in the photos above in the Data section. As we hypothesized before the experiment the front door handle location would lead to a colony with maximum growth due to frequent exposure to the student body and faculty. It is not surprising that the colony sample from the spatula has minimum growth, suggesting that the cafeteria employees were diligent in keeping the spatulas clean and hygienic. The possible sources of error in this experiment could be too much exposure of the growth medium to the air and inadvertent spillover from one quadrant to another quadrant. Based on my findings it is highly unlikely that the aforementioned sources of error would have affected my findings. A follow up experiment, which would further support our hypothesis, would be to sanitize the four locations and allow them to be exposed for a predetermined time period. The experiment then needs to be repeated with increasingly longer predetermined time periods. The results of this experiment would help us to determine the maximum bacterial density at each
location.
OR
As a follow up experiment it would be interesting to study the diversity of the bacterial colony. You would examine the colony under a light microscope and note the shapes of the bacteria, which would indicate whether they were coccus, bacilli, or spirillum.