User:Meghan E. Caul/Notebook/Biology 210 at AU

Lab Notebook Entry: Week #1

Meghan Caul 20 January 2015 BIO-210-005-2016S

On January 13, 2016, my group and I (group #3) observed a 20x20 transect located in between the outdoor amphitheater and Hughes Hall on American University's campus. Our assigned ecosystem is on a slightly tilted landscape and contains a man-made stream, a stepping stone pathway that continues through the stream, scattered deciduous trees, and a diversity of shrubs and other dwarf vegetation. Biotic components include: black squirrels running up the deciduous trees, brown birds (resembling finches) perched upon the branches of the deciduous trees, dwarf fern shrubs of a vibrant green color nestled into the topsoil, green wild onions sprouting from the topsoil adjacent to the stream, and green/black (mixed color) fungus located closer to the side of Hughes Hall. Abiotic components include: smooth gray and brown stones of various sizes tucked into both the centrality and meandering edges of the stream, stream water flowing in a downhill direction (due to tilted landscape), damp soil, or mud, on land adjacent to all edges of the stream, larger sized boulders (resembling granite) with rough texture make up stepping path, and fallen limb/bark/leaf pieces that scatter the entirety of the transect (due to Winter season).

Pictures of transect and its components:

Lab Notebook Entry #2

Meghan E. Caul 3 February 2016 BIO-210-005-2016S

Upon revisiting our group's (Group #2) Hay infusion culture on January 20,2016, a change in odor immediately presented itself. This worsening was most likely caused by bacterial proliferation that occurred in the week the culture was without contact. There was also a thick (1 cm) layer of sludgy mold floating atop the surface. It, along with the rest of the culture, also developed a darker pigmentation (opaque dark brown/black). We predicted the presence of Archaea in our agar plates to be unlikely because of our transect's lack of extreme temperature and soil salinity. However, If any were to be present they would most likely be identified as mesophiles due to the pollution within our transect. We later discovered a complete absence of Archaea. After preparing a total of 5 wet mounts containing a protozoa survey mixture (3 extracted from bottom of Hay Infusion jar and 2 from top--difference of one due a classroom cover-slip outage) and focusing under a 40x lens microscope, my group and I struggled to identify specimens due our culture being mostly devoid of life. We were, however, able to examine and identify many of the same species. This species, seeming to be the only kind in our Hay infusion, most closely resembled either Amoeba or ciliates and were intermittently motile. Additionally, we observed a bigger form that possessed an inner green ring but were unable to determine whether it was biotic or abiotic.

Agar plates treated with varying concentrations of tetracycline showed significantly more bacterial colonization and fungus that those within the control group (absence of tetracycline). These visible colonies appeared orange and blue in color and were most profuse within tet 10^-3 and tet 10^-5 agar plates (thousands of colonies) than in tet 10^-7 and tet 10^-9 agar plates ( a few dozen colonies). The agar plates lacking tetracycline treatment had minimal bacterial colonization and some translucent, fuzzy fungus.This data indicates bacteria present within the agar plates either are insensitive to the antibiotic used (tetracycline) or are antibiotic-resistant. Research demonstrates there are three mechanisms by which bacteria develop antibiotic resistance. These include tetracycline reflux, ribosome protection and tetracycline modification. It is important to also note that these mechanisms provide an increase in bacterial reproductive fitness and have been observed in both gram-positive and gram-negative bacteria. This further supports the claim that being antibiotic-resistant in an environment that allows for antibiotic exposure is beneficial to one's reproductive fitness. Diversely, tetracycline remains effective against specific intracellular bacterial pathogens (ex. Chlamydia).

Sources Cited: Antibiotic Resistance. (n.d.). Retrieved from http://www.antibioresistance.be/tetracycline/menu_tet.htmlSpectrum of Bacterial Susceptibility (n.d.). Retrieved February 01, 2016, from https://en.wikipedia.org/wiki/Tetracycline#Spectrum_of_bacterial_susceptibility

Pictures of examined specimens: