AP Biology Unknown Bacteria Lab Report

Bacteria Lab Report

INTRODUCTIONTrillions of bacteria inhabit the Earth, with some of them classified and some of them yet to be discovered. Often scientists work with bacteria that do not come in a labeled test tube, like for example, bacterial samples taken from infected human tissue or from the soil, and they must then identify the unknown microorganism in order to understand what behavior to expect from it, such as a certain type of infection or antibiotic resistance. However, because of the fewer forms of bacteria compared to animals, and because of the lack of bacterial fossil records due to their asexually reproductive nature, the taxonomy used to classify animals cannot be applied to bacteria (Brown 275). In order to classify unknown bacteria, a variety of physiological and metabolic tests are available to narrow a sample down from the fathomless number of possibilities into a more manageable range. Once these tests have been performed, the researcher can consult with a systematically arranged and continually updated collection of all known bacteria based on their structure, metabolism, and other attributes.The purpose of this experiment was to determine the bacteria sample you have grown from a specific part of the school, and then start testing its physical properties based on the resources we were given and told to do. We went to three places: the animal room, the gym, and the exercise room. We put our samples on three Petri dishes and waited for several days. The bacteria from the animal room grew the most, but yet the bacteria from the other two didnt grow that much. However, to me, of the three locations we visited, I believe the gym would be a place with a lot of bacteria, because the seats found all throughout the gym had a bunch of sticky, yucky pieces of gum and other strange substances on them, which is probably something that bacteria are attracted to. In addition, the gym had an odor, which could also be because of all the bacteria. However, my hypothesis was wrong about it and the animal room, as it seems, had the most bacteria. Now that we know that, we can start on determining what type of bacteria our sample is.

METHODSWe observed the organisms colony morphology by doing a straightforward procedure. To test for the presence of an extracellular lipopolysaccharide membrane, we were told to put the sample on a glass slide. After that, we put the glass slide facing the bacteria in the fire quickly, and then took it out fast, using the Bunsen burner. The heat-fixed smears were then created and Gram stained. The smears were stained with crystal violet for 90 seconds and then rinsed for 2 seconds. Then, we covered the mordant iodine for 60 seconds. After that, we decolorized the chemicals with 70% ethyl alcohol for 20 seconds, and then rinsed again for another 2 seconds. For the final step, we stained the slide with safranin for 60 seconds, and rinsed. We then blotted the back of the slide dry with paper towel, left the bacteria side alone, and examined it under a microscope for cell shape, as well as whether the cells stained Gram-positive (purple) or Gram-negative (pink). A pink stain would indicate an extracellular lipopolysaccharide membrane, whereas a purple stain would show a lack of this membrane. The shape, size, and color of the colonies were observed and recorded.

RESULTSTable 1 Gram Stain Test ResultsGram StainSimple Stain

Observationscells appeared pinkCells appeared a bit circular, and the groups of them were in large chunks

ResultGram-negativecocci

Table 1 shows the observations and results we came up with for the unknown bacteria. The Gram stain was performed several times to insure accuracy.

Figure 1 Basic Shapes of BacteriaFigure 1 shows the different forms of most bacteria. Our bacterium looks somewhat similar to a cluster of cocci, meaning the just one bacterium by itself is a coccus.

Figure 2 Shapes of Bacteria in Clusters or Groups

Figure 2 shows the names of clustered bacteria, or bacteria in groups. The unknown bacterium appears to take the staphylococcus shape since it is seen in chunks or clusters.

Figure 3 Actual Picture of the Bacteria

Figure 3 shows the actual picture of the bacteria we grew from our sample that was on the microscope. Notice how the bacterium is much clustered and somewhat circular and round.DISCUSSIONBased on the results we got, the bacteria would most likely fit in the Neisseria genus, because it is found mostly in chunks. We got our sample from an animal cage and this group of bacteria lives on animals, as well as humans. It also a normal type of bacteria that we encounter every day. In fact, 11 species of Neisseria live on humans, along with two of them, N. meningitidisandN. gonorrhoeae, being pathogens. When looking at the slide, the bacterium appears a bit circular, which could possibly mean that it has a staphylococcus shape. The bacterium was determined to be Gram-negative, because it had a basic pink color. This means that the bacterium has a lipopolysaccharide membrane. The texture seems very rough, and the size of each cell seems to be extremely small. You really cannot see the physical structure of one cell because of how small it looks. I think it could possibly be Neisseria, because it was Gram negative, very clustered, somewhat circular, and possibly because it is a type of bacteria that we are with throughout much of our lives. This was all of the basic data and results we could come up with. I really couldnt figure out what type of bacteria it is because we only tested one thing, the physical properties, and nothing else. Also, our bacterium was very close in a groups or chunks, so we really could not determine the shape of the bacteria. What we could have done in addition was to add pH or even in different environments to determine what it was. For example, we could tested the bacterias metabolic state to test whether the bacterium ferments sugars in order to produce ATP for energy, along with using tubes containing glucose, lactose, and mannitol that were inoculated and incubated. Another example would include determining the bacterias physiological characteristics, which included in testing the bacterias need for oxygen, and its growth depending on specific environments through pH or even temperature levels. These results would have been more formal than the results we had, like the enzyme lab we did, but it would have been more longer, but interesting to do as well. I also know that we would probably no time to those suggested experiments, but it would have been a much more professional way to classify the bacteria that we grew.

RESOURCES1. Brown, Alfred E. Bensons Microbiological Applications: Laboratory Manual in General Microbiology, Short Version, Eleventh Edition. New York: The McGraw-HillCompanies, Inc., 2009. Print.2. Hensyl, William. Bergey's Manual of Determinative Bacteriology. Baltimore: Lippincott Williams and Wilkins, 2000. Print.3. "Bacteria."Microbiology Online. Society for General Microbiology. Web. 16 Dec. 2014. 4. "Bacteria Basics - They Are Alive!"Biology4Kids.com: Microorganisms: Bacteria. Andrew Rader Studios. Web. 20 Dec. 2014. 5. "Streptococci and Oral Streptococci."Bite Sized Tutorials, Streptococci and Oral Streptococci. Newcastle University. Web. 21 Dec. 2014. 6. "The Size, Shape, And Arrangement Of Bacterial Cells."Functional Anatomy Of Prokaryotic And Eukaryotic Cells. Midlands Technical College. Web. 21 Dec. 2014.