Bacteria are the most widely distributed organisms in the biosphere. They are found in all different types of soil, water and even in the bodies of other living organisms. Every single place that humans have explored on the Earth, have shown to contain microbes. Bacteria are living organisms and like all living organisms, they require energy and carbon sources in order to metabolize and reproduce. And like all living organisms they respond to changes in their environment. Ubiquity is defined as the state of being everywhere all the time. In this lab you will test the idea that microbes are ubiquitous or present everywhere at all times.
One Triptic Soy Agar (TSA) plate per student
One sterile swab
1. Decide on an area to test for the ubiquity of microbes. List your area on the white board in front of the classroom. 2. Obtain one TSA plate and label it on the bottom (side with the agar) with your name, class section and the surface you will sample. 3. Obtain one sterile swab.
4. To obtain a sample, roll the sterile swab back and forth across the area you wish to sample. If the area you are sampling is dry, you will need to wet the swab with distilled water before you obtain a sample from that area. 5. To inoculate the agar, roll the swab gently across the surface of the agar plate. Do not break the surface of the agar. 6. When you are finished, dispose of the swab in the biohazard container and place the inoculated TSA plate upside down in the 37°C incubator. 7. Incubate the plates for 48 hours.
8. After incubation, observe the plates for microbial growth
1. Analyze your plate. (Evaluate the types and numbers of colonies on your plate, and make a conclusion as to why this type of result came from that particular source.) The plate contained no growth after 48 hours of incubation. There could be many different factors that could have affected the growth. 2. Analyze the results of the White Board plate.
The plate contained no growth after 48 hours of incubation.
3. Analyze the results of the Toilet plate.
The toilet plate contained numerous colonies throughout. Its shape was punctiform and translucent white.
4. Analyze the results of the Mouth plate
There was an abundance of growth on the plate and colonial diversity as well. The bacterial growth was circular and contained a yellowish opaque color. Differential colors in bacterial growth can be determined by temperature or nutrient supply. 5. You sampled the bottom of your shoe and your lab partner sampled behind his ear. The two very different surfaces have produced similar colonies on the plates. Explain how this could happen. Similar colonies from different sources can be a result of their control environment. The characteristics that are observed are determined by controlling the nutrient broth on the agar plates, same incubation period, same incubation area or even contamination. Both plates could have been contaminated by the environment during their incubation growth which resulted in similar bacterial growth.
6. Another student in the class performed the procedure for this experiment perfectly, yet 48 hours after incubation there were no discernible colonies on the plate. Give two different reasons to explain these results. One reason is that bacteria could have been dead already. The bacteria usually looks the same dead or alive, this can affect the assumption of whether or not the cells on the agar or in a broth or alive. Another reason is that depending on where the bacteria were from, it might be on plate but growing very, very slowly. Bacterial growth can grow rapidly if their needs are met but if they are not provided with their optimal growth conditions then they will grow much slower.